Enable cinder-manage to remove services

Enable cinder-manage to remove services

These changes are to enable cinder-manage to remove old services
from the database like nova does. All that is being added is the remove
method to manage.py and tests to cover this new method in test_cmd.py.
The command will remove the binary from the list of running services
in the db that can be viewed via "cinder-manage service list". NOTE:
Active and restarted services will re-populate the DB with their current
status automatically.

To use this new command, the user types "cinder-manage service remove
<binary> <host>" and the service will be removed.

DocImpact

Change-Id: I3bcec824d3c5f65fdd187459428025993a2010a0
Implements-blueprint: add-cinder-service-removal