More conductor support for resizes

This patch adds more support for resizes to conductor, which apparently
are not getting tested in the "full" tempest gate.

This adds network_migrate_instance_{start,finish}() calls to conductor,
which offloads the network_api calls of similar name over RPC for
components that can't take the DB hit of calling network_api directly.
Also, in quota, the commit and rollback calls hit the database, so
export those from conductor as well.

This is likely the source of the failures in bug 1119817

Change-Id: I56bb65b0e168e36e138cf6bf125d6e83bf71f50b
Merge "More conductor support for resizes"