Currently the Nova API container does all the database bootstrapping
for Nova. In a deployment with more than one active cell, it makes
more sense for the conductors to bootstrap their own databases, rather
than have the Nova API container do it. This change adds support for
that. Until the support is actually used, we leave Nova API as-is.
Partially Implements: blueprint support-nova-cells
Change-Id: Id3a78b6838a3aae04f5dd5bd6ec928359297cfd3
b087f058c9