php: Add GetObject, PutObject, MultipartUpload tests

[krisis]

• Made cleanup to run even when test fail using finally block.
• Randomized bucket names to avoid collision across SDK tests.

[nitisht]

@krisis I tried running the tests on localhost with Minio server container running, I get the below error in aws-sdk-php/error.log

PHP Notice:  Use of undefined constant http_ok - assumed 'http_ok' in /mint/run/core/aws-sdk-php/quick-tests.php on line 266
PHP Fatal error:  Uncaught exception 'Aws\S3\Exception\S3Exception' with message 'Error executing "DeleteBucket" on "http://127.0.0.1:9000/aws-sdk-php-bucket-14023"; AWS HTTP error: Client error: `DELETE http://127.0.0.1:9000/aws-sdk-php-bucket-14023` resulted in a `409 Conflict` response:
<?xml version="1.0" encoding="UTF-8"?>
<Error><Code>BucketNotEmpty</Code><Message>The bucket you tried to delete is not  (truncated...)
 BucketNotEmpty (client): The bucket you tried to delete is not empty - <?xml version="1.0" encoding="UTF-8"?>
<Error><Code>BucketNotEmpty</Code><Message>The bucket you tried to delete is not empty</Message><Key></Key><BucketName></BucketName><Resource>/aws-sdk-php-bucket-14023</Resource><RequestId>3L137</RequestId><HostId>3L137</HostId></Error>'

Exception: copyobject api failed for aws-sdk-php-bucket-14023 in /mint/run/core/aws-sdk-php/quick-tests.php:267
Stack trace:
#0 /mint/run/core/aws-sdk-php/quick-tests.php(339): testDeleteObjects(Object(Aws\S3\S3Client), 'aws-sdk-php-buc...', 'obj1')
#1 {main}

Next in /mint/run/core/aws-sdk-php/vendor/aws/aws-sdk-php/src/WrappedHttpHandler.php on line 192

[nitisht]

Please fix the test issues as commented.

[krisis]

@nitisht I have fixed the runtime error.

[nitisht]

There is one test case failure with PHP tests - related to Minio Server FS issue (minio/minio#4625)