Suppress retries on UnexpectedTaskStateErrors

Don't try to re-schedule if an UnexpectedTaskStateError occurs during
a build.  If the instance was deleted mid-build, just catch the
exception and log a message.

Change-Id: I5e577f252ee71f310a749186060808723b676854
Merge "Suppress retries on UnexpectedTaskStateErrors"
Merge remote-tracking branch 'm_src_repo/master' into build-temp