Remove hearbeat sent to the neutron

[rajiv]

This bug is to track the effort for
==> Neutron enhancement (Check RFE)(rajivk)
    - agentdb/agentapi: allows no timeout
    - initialization hook

For the agentdb/agentapi item, the thing is currently agentdb sort of maintaining an DB item for each agent. Each agent has to maintain a heartbeat with neutron server. If timed out, the agent item in agent DB will be marked out to be not usable.
In our case, ODL is agentless. In order to adopt this agentDB model, we faked one in networking-odl. And in this fake agent, we maintain heartbeat with neutron server. This heartbeat is not necessary for ODL since all the node status is maintained by ODL. In theory, once ODL discovers a node is down, it will inform networking-odl which will relay this information to agentdb to mark it down.

This bug is to remove the part, where neutron server is notified regarding node failure and constant updates are sent.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/452625

[Isaku Yamahata (yamahata)]

There are two aspect, port binding and agent liveness report.
Regarding to port binding, in networking-odl, there is websocket logic and prepopulate logic. with them we don't use polling loop to update agentdb.

Regarding to agent liveness, ml2 driver has agent health check by timer.
self.add_agent_status_check_worker(self.agent_health_check)
it causes annoying log message warning agetn is dead.
and via agent api, cloud admin can get a list of agent. the admin will be surprised by many (wrongly) dead ODL pseudo agent.

[OpenStack Infra (hudson-openstack)]

Change abandoned by Armando Migliaccio (<email address hidden>) on branch: master
Review: https://review.openstack.org/452625
Reason: This review is > 4 weeks without comment, and failed Jenkins the last time it was checked. We are abandoning this for now. Feel free to reactivate the review by pressing the restore button and leaving a 'recheck' comment to get fresh test results.