Allow resources to be updated in parallel

Turn Resource.update() into a coroutine.

Change-Id: I625a2d81095cc28161f8e2342121bfe1939611e3
Parallelise Instance updates

Change-Id: I358f7fbdb3232f4bf528d170476935ef2b4239cc
Merge "Allow resources to be updated in parallel"
Merge "Parallelise Instance updates"