Graceful shutdown in Queue Length Providers

[tmasternak]

For some queue length providers, shutting down the endpoint causes

2018-10-04 12:28:53.5824|41|Error|ServiceControl.Transports.SQLServer.QueueLengthProvider|Error querying sql queue sizes.
System.Threading.Tasks.TaskCanceledException: A task was canceled.
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at ServiceControl.Transports.SQLServer.QueueLengthProvider.d__14.MoveNext() in C:\BuildAgent\work\75ab57c3309c2d4a\src\ServiceControl.Transports.SQLServer\QueueLengthProvider.cs:line 141
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at ServiceControl.Transports.SQLServer.QueueLengthProvider.d__13.MoveNext() in C:\BuildAgent\work\75ab57c3309c2d4a\src\ServiceControl.Transports.SQLServer\QueueLengthProvider.cs:line 130
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at ServiceControl.Transports.SQLServer.QueueLengthProvider.<b__10_0>d.MoveNext() in C:\BuildAgent\work\75ab57c3309c2d4a\src\ServiceControl.Transports.SQLServer\QueueLengthProvider.cs:line 75

to be logged even though this is users action that caused that. We should handle this scenario gracefully.

[danielmarbach]

Given that we are about to release 2.1 I gave this a quick shot, see #175

[danielmarbach]

Addressed in #175 . Closing