dipose method is fully deprecated on neutron.db.api module

[Kyle Haley]

In neutron/db/api.py, the dispose method is no longer utilized.
It works in neutron.679.11, because neutron.679 is on version 9.0.0.0rc2
https://github.com/openstack/neutron/blob/c9a54002f2fdbd86e03fb266361ff482ea1c6c9f/neutron/db/api.py#L203-L205
In the version we're on, 10.0.0.0rc2, this is not the case:
https://github.com/openstack/neutron/blob/10.0.0.0rc2/neutron/db/api.py
The dispose method should no longer be called on the neutron.db.api module defined as "session" in the below code:
    def serve_rpc(self):
        """Launches configured # of workers per loaded plugin."""
        if cfg.CONF.QUARK_ASYNC.rpc_workers < 1:
            cfg.CONF.set_override('rpc_workers', 1, "QUARK_ASYNC")

        try:
            rpc = service.RpcWorker(self.plugins)
            session.dispose() # probaby not needed, but maybe
            launcher = common_service.ProcessLauncher(CONF, wait_interval=1.0)
            launcher.launch_service(rpc, workers=CONF.QUARK_ASYNC.rpc_workers)

            return launcher
        except Exception:
            with excutils.save_and_reraise_exception():
                LOG.exception(_LE('Unrecoverable error: please check log for '
                                  'details.'))

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/500947

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/500947
Committed: https://git.openstack.org/cgit/openstack/quark/commit/?id=92fa456c71076f47a0442fc5df6bf49d73b92c4a
Submitter: Jenkins
Branch: master

commit 92fa456c71076f47a0442fc5df6bf49d73b92c4a
Author: Kyle Haley <email address hidden>
Date: Tue Sep 5 11:03:46 2017 -0700

    Removing deprecated dispose method call

    The dispose method call against neutron.db.api has been removed in this
    iteration of neutron (Ocata). Removing this call as it may not have ever
    been needed based on the accompanying comment on that line.

    Change-Id: I3d8c5d50650abda8064eb860118ae2e40d3662a5
    Closes-Bug: 1714536