There should be a check in place when adding a volume that is already in a CG to a new CG

[Alex O'Rourke]

Currently, if you take a volume that belongs to a consistency group and add it to a new consistency group, it will remove it from cg1 and place it in cg2 without warning. It gives the feeling the volumes belongs to two CGs and it also allows for a user to unintentionally remove the volume from its original cg and place it in a new cg without even knowing.

There should be a check in place that will not allow you to add a volume to a cg if it is already in a different cg until you delete it from its original cg. We should raise InvalidConsistencyGroup telling the user to first delete the volume from the cg before adding it to a new cg.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/215262

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/215262
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=b9f7825ea6fc3f6ea213627631e7d64b655074bf
Submitter: Jenkins
Branch: master

commit b9f7825ea6fc3f6ea213627631e7d64b655074bf
Author: Xing Yang <email address hidden>
Date: Tue Aug 11 23:09:30 2015 -0400

    Prevent volume already in CG to be added to another

    If a volume is already in a CG, currently it can still be added to
    another CG without any warning. We should add a check to see if the
    volume is already in a CG and prevent it from being added to another
    if that check returns True. It has to be removed from the previous
    CG in order to be added to a new one.

    Change-Id: I6ec92cbf4ce60e7afbfa5a57edef18ddba554a74
    Closes-Bug: #1487151