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
Default video type to 'vga' for PowerKVM

PowerKVM currently doesn't support 'cirrus' video type. For now, we can
detect if Nova compute is running on ppc64 or ppc architecture systems
and set the default to 'vga', which is supported on PowerKVM.

This patch did some reordering of the logic in
nova.virt.libvirt.driver.LibvirtDriver.get_guest_config in an attempt to
set the video.type depending on the compute host architecture and
implementation specifics. The video.type can still be set using
image_meta.

Change-Id: I49a1a8e6d9ebdc28d876d2f958c8cb960892f322
Closes-Bug: 1274367
Merge "Default video type to 'vga' for PowerKVM"
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"
Merge "XenAPI: Monitor the GC when coalescing"
Merge commit 'refs/changes/08/60808/6' of git://gold.eng.hq.xensource.com/git/github/openstack/nova into tmpbranch
Merge commit 'refs/changes/97/66597/4' of git://gold.eng.hq.xensource.com/git/github/openstack/nova into tmpbranch
Merge commit 'refs/changes/79/69879/3' of git://gold.eng.hq.xensource.com/git/github/openstack/nova into tmpbranch