nova: use RequestContextSerializer for notifications

RequestContext should be serialized when sent via oslo.messaging. The
serializer is correctly used for the general RPC mechanism, but has been
forgotten in the notifier. This patch fixes that.

Change-Id: I56fa8022e34c0e80835e3bde940fda99ed0f9ba8
Closes-Bug: #1275771
Typo in backwards compat names for notification drivers

The switch to oslo.messaging uses setup.cfg to provide a mapping
for the Nova notification drivers, but mis-spelt them.   This will
break any existing Nova systems that use notifictaions for things
like billing, monitoring, etc

Change-Id: I217d6b68a64ee008a82426b890a32a97b849cb4d
Merge "nova: use RequestContextSerializer for notifications"
Merge "Typo in backwards compat names for notification drivers"