Gracefully handle qpid errors

If a qpid error occurs when Glance is sending notifications, the
qpid connection may not be cleaned up properly.  This change catches
qpid exceptions to allow proper error handling.

Fixes bug 1164681

Conflicts:
	glance/tests/unit/test_notifier.py

(cherry picked from commit 1e98e108c057914a1e8b2ee2295c80db410b5ffa)
Change-Id: Ica3ef54b958e4efe3932b90d721324e7860b1ea4