Merging linuxbridge support from pebbles:

Enable quantum linuxbridge support for nova

When running nova with quantum on linuxbridge plugin nova compute should
be aware of it to create appropriate interfaces for vms. This patch
sets libvirt_vif_driver and linuxnet_interface_driver in nova.conf.
Add all nova-compute related options to nova.conf

This removes the need to have a separate nova-compute.conf on the compute
nodes. On Ubuntu systems a static nova-compute.conf is installed that just
contains comments to document this change. (This is also what the upstream
stackforge cookbooks do)
Merge pull request #228 from cdearborn/pull-req-release-mesa-1.6.1-master-2e7e34caa12af20d403f9baa19e5050351e2b7d9

Merging Linux bridge support into Mesa 1.6.1 [3/3]