CSX Tests can occasionally fail with "Cannot enqueue data after PromiseNotToEnqueue"

Occasionally we've seen CSX tests fail because of the issue described here :

https://github.com/Azure/azure-functions-host/issues/999

The host starts up fine, but then any functions that failed compilation in this way are not actually started, with the result that there will later on be failures such as this:

`Http request failed with code NotFound. Please check output for more detailed message.`

Since there isn't an actual fix it seems the solution here would probably be to watch for that message in the startup output, and if we see it kill the process and retry startup.