fixed concurrency and added unit tests

[johnataylor]

fixes #1292

• removed caching of container handle
• removed concurrency from Delete, Read and Write calls
• simplified code it use straight forward loops instead of Linq and Lambdas
• fixed conditional creation of AccessCondition (the original code was non sense but probably harmless)
• removed calls to IfExists for container on Delete and Read (which are coded to be conditional anyhow)
• added unit tests

This should most likely fix the non-nonsensical ETag exception because this code was incorrect. At least this code is now correct and that should presumably make the exception go away, at least it's a start. Anyhow I could not reproduce this exact problem either way.

I also made a good start on adding unit tests, I'm sure we could always add more.

[cleemullins]

+1 to use of Cancellation Token here.

Should you be checking between iterations to see if it was cancelled, then bail out? Or does that happen automatically through Exception handling?

[cleemullins]

Build error:

2019-02-12T19:37:41.9675561Z Failed   TestBlobStorageWriteRead
2019-02-12T19:37:41.9702014Z Error Message:
2019-02-12T19:37:41.9702191Z  Test method Microsoft.Bot.Builder.Azure.Tests.AzureBlobStorageTests.TestBlobStorageWriteRead threw exception: 
2019-02-12T19:37:41.9704722Z Microsoft.WindowsAzure.Storage.StorageException: No connection could be made because the target machine actively refused it ---> System.Net.Http.HttpRequestException: No connection could be made because the target machine actively refused it ---> System.Net.Sockets.SocketException: No connection could be made because the target machine actively refused it
2019-02-12T19:37:41.9704849Z Stack Trace:
2019-02-12T19:37:41.9704899Z     at System.Net.Http.ConnectHelper.ConnectAsync(String host, Int32 port, CancellationToken cancellationToken)
2019-02-12T19:37:41.9704985Z --- End of inner exception stack trace ---
2019-02-12T19:37:41.9705033Z     at System.Net.Http.ConnectHelper.ConnectAsync(String host, Int32 port, CancellationToken cancellationToken)
2019-02-12T19:37:41.9705077Z    at System.Threading.Tasks.ValueTask`1.get_Result()
2019-02-12T19:37:41.9705146Z    at System.Net.Http.HttpConnectionPool.CreateConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken)
2019-02-12T19:37:41.9705540Z    at System.Threading.Tasks.ValueTask`1.get_Result()
2019-02-12T19:37:41.9705601Z    at System.Net.Http.HttpConnectionPool.WaitForCreatedConnectionAsync(ValueTask`1 creationTask)
2019-02-12T19:37:41.9705644Z    at System.Threading.Tasks.ValueTask`1.get_Result()
2019-02-12T19:37:41.9705693Z    at System.Net.Http.HttpConnectionPool.SendWithRetryAsync(HttpRequestMessage request, Boolean doRequestAuth, CancellationToken cancellationToken)
2019-02-12T19:37:41.9705761Z    at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
2019-02-12T19:37:41.9705910Z    at System.Net.Http.HttpClient.FinishSendAsyncUnbuffered(Task`1 sendTask, HttpRequestMessage request, CancellationTokenSource cts, Boolean disposeCts)
2019-02-12T19:37:41.9705982Z    at Microsoft.WindowsAzure.Storage.Core.Executor.Executor.ExecuteAsync[T](RESTCommand`1 cmd, IRetryPolicy policy, OperationContext operationContext, CancellationToken token) in C:\Program Files (x86)\Jenkins\workspace\dotnet-split-pr-master\Lib\ClassLibraryCommon\Core\Executor\Executor.cs:line 93
2019-02-12T19:37:41.9706059Z --- End of inner exception stack trace ---
2019-02-12T19:37:41.9706124Z     at Microsoft.WindowsAzure.Storage.Core.Executor.Executor.ExecuteAsync[T](RESTCommand`1 cmd, IRetryPolicy policy, OperationContext operationContext, CancellationToken token) in C:\Program Files (x86)\Jenkins\workspace\dotnet-split-pr-master\Lib\ClassLibraryCommon\Core\Executor\Executor.cs:line 256
2019-02-12T19:37:41.9706230Z    at Microsoft.WindowsAzure.Storage.Blob.CloudBlobContainer.CreateAsync(BlobContainerPublicAccessType accessType, BlobRequestOptions options, OperationContext operationContext, CancellationToken cancellationToken) in C:\Program Files (x86)\Jenkins\workspace\dotnet-split-pr-master\Lib\ClassLibraryCommon\Blob\CloudBlobContainer.cs:line 179
2019-02-12T19:37:41.9706343Z    at Microsoft.WindowsAzure.Storage.Blob.CloudBlobContainer.CreateIfNotExistsAsync(BlobContainerPublicAccessType accessType, BlobRequestOptions options, OperationContext operationContext, CancellationToken cancellationToken) in C:\Program Files (x86)\Jenkins\workspace\dotnet-split-pr-master\Lib\ClassLibraryCommon\Blob\CloudBlobContainer.cs:line 383
2019-02-12T19:37:41.9706422Z    at Microsoft.Bot.Builder.Azure.AzureBlobStorage.WriteAsync(IDictionary`2 changes, CancellationToken cancellationToken) in D:\a\1\s\libraries\Microsoft.Bot.Builder.Azure\AzureBlobStorage.cs:line 160
2019-02-12T19:37:41.9706500Z    at Microsoft.Bot.Builder.Azure.Tests.AzureBlobStorageTests.TestBlobStorageWriteRead() in D:\a\1\s\tests\Microsoft.Bot.Builder.Azure.Tests\AzureBlobStorageTests.cs:line 41

[coveralls]

Pull Request Test Coverage Report for Build 48999

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 10 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+1.7%) to 74.772%

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Files with Coverage Reduction	New Missed Lines	%
/libraries/Microsoft.Bot.Builder.Azure/AzureBlobStorage.cs	10	73.08%

Totals
Change from base Build 48899:	1.7%
Covered Lines:	4022
Relevant Lines:	5379

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💛 - Coveralls