Close HttpWebRequest's response stream on WebExceptions

[lewislabs]

If httpRequest.GetResponse() internally throws a WebException then there is still a response stream to close. I believe this is causing sockets to remain open and leading to #152

[gokarnm]

Hi @lewislabs , thanks for the PR! I'll go through the change, test it and get back you.

[lewislabs]

Thanks @gokarnm. I think these commits could also go into master. Let me know what you think.

[gokarnm]

Hi @lewislabs , the changes look good! I'm curious about how you tested this, specifically WriteContentToRequestBody() throwing an exception leading to CompleteFailedRequest() being called.

[lewislabs]

Hi @gokarnm. I haven't tested this explicitly, I'm primarily going on this comment here https://github.com/aws/aws-sdk-net/blob/master/sdk/src/Core/Amazon.Runtime/Pipeline/HttpHandler/HttpHandler.cs#L98

If the httpRequest.GetResponse() call throws an exception (more than likely a WebException) then the response variable will be null and will not be disposed. If you don't dispose of the response stream then this will leave a socket open in CLOSE_WAIT state and will keep hold of one of the connections from the ServicePoint's pool. If this happens a few times then you run the risk of using up all the sockets available to the ServicePoint and any subsequent httpWebRequest.GetResponse() calls will simply block forever.