Fix _error_out_instance exception handler

Since Eventlet clears exceptions between greenthread switching, we need
to save that exception so it can be re-raised.

The _error_out_instance event handler did not wrap the quotas call with
the save_and_reraise_exception, so the original exception was lost.

Fixes bug 1163552

Change-Id: I69d28917aae1d787351cd800f8996532e5485eb2
Merge "Fix _error_out_instance exception handler"