Make compute manager use conductor for stopping instances

During _sync_power_states, the manager will call to compute_api to
stop instances as necessary. This takes a database hit, which isn't
allowed. This directs that call through conductor, following the
pattern of late.

Fixes bug 1123219

Change-Id: I5d789dd73390cb1c41a245f6594b1c3aecf7efde
Add API sample tests to Services extension

Partially implements blueprint nova-api-samples
Bug 1091755

Change-Id: I7a0e124871c248bbb7613bfcdf335fee29a887f2
Merge "Make compute manager use conductor for stopping instances"
Merge "Add API sample tests to Services extension"