Prevent nova services' coverage data from combining into nova-api's

Now if combining a coverage report once, nova services' coverage
data are combined into nova-api's.
This renames nova-api coverage datafile to .nova-coverage.api and
creates a new coverage instance to combine when reporting.

Fixes bug: 1152475

Change-Id: I90b6535d490cf0123a127f8752986edd782ef37e
baremetal: Drop unused columns in bm_nodes

Drop these two columns:
* bm_nodes.prov_vlan_id
* bm_nodes.registration_status

And update related code, tests and api_samples.

Change-Id: Iadefc83a00ad9ae5a3bb39f357080299875bdf09
Add unit tests for nova.volume.cinder.API

Fixes bug 1042215

Change-Id: I281f56c5a247b4af4e91182be13f5fcd6772917c
Merge "Prevent nova services' coverage data from combining into nova-api's"
Merge "Add unit tests for nova.volume.cinder.API"
Merge "baremetal: Drop unused columns in bm_nodes"