Sync with oslo-incubator

Modules held back:

- openstack.common.policy. Bug #1268315.

Compatibility changes made:

- Additional arguments added to the Context object
- RPC Services no longer need to explicitly wait on
  the rpc consumer thread
- Our openstack-common.conf file explicitly includes
  transitive dependencies. This is no longer necessary.
  Bug #1268314.

Additional changes still necessary:

- We use some depreciated modules (WSGI), we need to remove
  our dependence on these. Bug #1268313.

Change-Id: Ia52b386a928e1d03709dfdb23f0d504c7d01bc19
Oslo-SHA1: 8710dbacfd7d8dad58fccbdd4ffda7246dcbbb7c
Closes-Bug: 1268314
Reinstate RecordSet placement validation

Change-Id: I3e8ea08e73739a401ea111de583bfcbf4a3e0a2f
Closes-Bug: 1268327