V2 RpcApi should register when db pool is enabled

The rpc api controller registers the public methods of db_api
But, use_tpool is True, the thread pool wrapper's methods are
used which would lead to failures.

Fixes Bug #1221037

Change-Id: Iaba10178c7da1548257e2180658c2dc8ba3e048b
Correct documentation related to protected properties

Fixes bug 1233303

Specified conditions under which glance api will not start
successfully.

DocImpact

Change-Id: I8498e9e51f5c7e0d411379c0574c0b8e300f77c2
Add call to get specific image member

Fixes bug 1233806

Add GET call to get a specific image member. Makes it easier to
check image member status

DocImpact

Change-Id: I63039bc15d2045fbceb71cae56225a9ee9eecd51
Merge "Correct documentation related to protected properties"
Updated from global requirements

Change-Id: I4f26d3a8790c799e5c1f7f81031406e0c57545f9
Enable tasks data model and table for async worker

Add tasks data model and table for async worker to
store the tasks data persistently.

Partially implement blueprint async-glance-workers

Change-Id: I2b2d70295da4905bf75cffc2b2eadec174d1abfc
Merge "Add call to get specific image member"
Merge "V2 RpcApi should register when db pool is enabled"
Merge "Updated from global requirements"