Properly preserve trace on error during wait

This commit starts using save_and_rereraise_exception from oslo
excutils when handling an server ERROR state during a wait loop.
Previously, if the wait loop in the common api create_server method
caught a BuildErrorException it attempts to do some final processing
and cleanup around that server. However, doing this interferes with
the trace output from the failure and only would show the subsequent
re-raise as the stack trace. This commit avoids that but using the
oslo method to get around this.

Change-Id: I62193af963020311d5ed90a847c9764faff3e4c2
Merge "Properly preserve trace on error during wait"