Added new response mocking behavior (#10976)
Added new response mocking behavior (#10976)

WithSlowResponse() to simulate a slow HTTP response.
WithBodyReadError() returns an HTTP response that fails when reading the
body.
Fixed a bug with writing response headers.
Azure/azure-sdk-for-go,Azure/azure-sdk-for-go,Azure/azure-sdk-for-go,Azure/azure-sdk-for-go