restapi: Migrates the brick data and mark it for deletion

Migrates the brick data to other existing bricks and marks the brick
for deletion.

Usage:
    - api/clusters/<cluster-Id>/glustervolumes/<volume-id>/bricks/migrate

Input Parameters:
    <action>
        <bricks>
            <brick>
                <name><Brick1-Name></name>
            </brick>
            <brick>
                <name><Brick2-Name></name>
            </brick>
        </bricks>
    </action>

Change-Id: Iaa88f3402a25316d1717ee914aa77856fbe802db
Signed-off-by: Shubhendu Tripathi <shtripat@redhat.com>