Policy check for forced_host should be before the instance is created

Move the policy enforcment for force_host and force_node into the
_handle_az() method so that any violation of policy is detected before
the DB entry for the instance is created.

Fixes bug: 1220220

Change-Id: Iaf6df4f8df6cca71fcb860244ccf758d7908b8f1
Add notification for pause/unpause instance

When pause/unpause instance, there are no notifications, this
will cause someone cannot know when pause/unpause operation
would be finished.

All other instance operations do have notifications. We should
also add notification support for those two operations.

Change-Id: I5b8cc33a5992f5f028a3220217dcf7a0288d150d
Closes-Bug: #1043861
Full sync of quota_usages

Migration 203 added a user_id column to the quota_usages table.  Now
some usages are incremented/decremented on a per user basis but there
are preexisting usages stored with a NULL user, and some usages are
tracked per project but there are usages stored with a user_id.  These
quotas are never decremented leading to invalid quota limits being
enforced.

This migration performs a full sync of quotas, and removes the incorrect
rows for each resource type.

Change-Id: Iff96f81e36b135df94a6f25c9443d0e9333bd18f
Closes-Bug: #1212798
Merge "Full sync of quota_usages"
Merge "Policy check for forced_host should be before the instance is created"
Merge "Add notification for pause/unpause instance"