Remove some db calls from db servicegroup driver.

The base service code already ensures that a service record is created.
Store that in the service object.  Then down in the servicegroup db
driver, access it instead of having to go look it up again.

Part of bp no-db-compute.

Change-Id: Ife3c98c29c6f654585e14ded5a9b4c7e3bec226d
Add service_update to conductor.

Add a service_update method to the conductor API.  This will be
necessary for removing direct db access from the servicegroup db driver.

Part of bp no-db-compute.

Change-Id: Ic9a205ed4e810ee3511378742f764b2b311174a7
Use conductor in the servicegroup db driver.

This patch updates the servicegroup db driver to use the conductor API
in the cases where it was accessing the db directly before.  If the
service is allowed to do direct db access, the conductor API will
optimize the call to go straight to the db.  Otherwise, it will invoke
rpc to a remove conductor service to perform the operations.

Part of bp no-db-compute.

Change-Id: I96adffc6f80288c829d84f170414613a35b5c840
Merge "Remove some db calls from db servicegroup driver."
Merge "Add service_update to conductor."
Merge "Use conductor in the servicegroup db driver."