Change arguments to volume_detach()

Most compute API calls accept an instance object.  To be compatible with
cells, volume_detach() should as well.  Also change it to accept the
volume object, instead of just a volume ID.  This lets us proxy the
volume object to child cells a bit more easily.

This removes 2 skipTests that we have related to volumes and cells.

Fixes bug 1157408

There was also a check that if instance_get_by_uuid() returned no
instance, it VolumeUnattached should be raised.  However, this check
would never work as InstanceNotFound would have been raised.  This
patch also corrects that.

Change-Id: Ide35ad5d8e147f6bd21b5840b901363dab0eae38
Cells: Add support for global cinder

Implements cinder support for compute cells when cinder is a global
installation.  Adds syncing of the block device mapping table between
child cells and API cells.

Implements blueprint cells-cinder-support

Change-Id: Ife5be9922db0742c8ee4f970517396be86597cce

Conflicts:

	nova/cells/manager.py
	nova/cells/rpcapi.py
	nova/db/sqlalchemy/api.py

Conflicts:
	nova/cells/manager.py
	nova/cells/messaging.py
	nova/cells/rpcapi.py
	nova/tests/cells/test_cells_manager.py
	nova/tests/cells/test_cells_messaging.py
	nova/tests/cells/test_cells_rpcapi.py
Fix up cinder support tests

Change-Id: I947bb9f2ea1dc15958eeee5709803096b44b5c26
Only allow volume attaching in the same AZ

Change-Id: I0f7b8fa8740c8f194174ee089cf6de1883267757