servicegroup.API.leave() method is unused

[Jay Pipes]

The nova.servicegroup.API.leave() method is not used by anything. It should be removed.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/149923

[OpenStack Infra (hudson-openstack)]

Change abandoned by Jay Pipes (<email address hidden>) on branch: master
Review: https://review.openstack.org/149925

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/149923
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=7c387637614871fac460955c0ea3beb139ae168c
Submitter: Jenkins
Branch: master

commit 7c387637614871fac460955c0ea3beb139ae168c
Author: Jay Pipes <email address hidden>
Date: Sun Jan 25 16:56:47 2015 -0800

    Fix up join() and leave() methods of servicegroup

    The join() method was not documented properly, and the Zookeeper
    driver's implementation of the join() method returned a FakeLoopingCall
    object for no reason whatsoever (the other drivers just return None), so
    it's not necessary.

    The leave() method wasn't used anywhere at all, therefore this patch
    removes it entirely.

    Change-Id: Idbd95636dbebfb4f21a25d23625ee338c1ba863e
    Closes-bug: #1414513
    Closes-bug: #1414515