Bump to sqlalchemy-migrate 0.8.2

This allows us to drop some unsightly
0.7.3 patching and also avoids potential
issues in using 0.8.1 which had a bad
release version string (it was called '0.7.3dev' by mistake).

This will require a requirements change here:

 https://review.openstack.org/56662

Change-Id: I5f80dfc07f8256716d025002fc1a1f47e58b2142
Closes-Bug: 1251700
Change ConductorManager to self.db when record cold_migrate event

In conductor manager, when cold migrate an instance, conductor
manager will record event of cold_migrate.

When record this event, conductor manager pass ConductorManager but
not self.db as parameter for compute_utils.EventReporter(), as we
can access the db directly from conductor manager so going through
ConductorManager as a proxy is unnecessary.

Change-Id: Ic52228c2550294c2df37d10d36637e4d0e3a1a30
Merge "Bump to sqlalchemy-migrate 0.8.2"
Merge "Change ConductorManager to self.db when record cold_migrate event"