Simplify l2pop driver code

[venkata anil]

Simplify l2pop driver code.

l2pop driver unable to properly decide about port add/remove notifications when it gets called with different port status from nova and l2 agents through different workers during instance migrations.
There were many suggestions to modify the port status in plugin(some suggested to change it to BUILD, some reviewers to DOWN, etc ..) during migration(see the comments in https://review.openstack.org/#/c/215467/ ), so that l2pop can properly decide about port's binding host based on status. Deciding about which status to set to port in plugin and using the same in l2pop driver is confusing, and reviewers giving different opinion(comments in https://review.openstack.org/#/c/215467/ ).

Kevin suggested that l2pop shouldn't depend on port status for deciding about host. Instead it should use binding info in db, which reviewers of the patch( https://review.openstack.org/#/c/215467/) agreed.

note: There was a separate bug https://bugs.launchpad.net/neutron/+bug/1555600 reported for "agents fail to create flood flows with multiple workers"

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/269212

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/288284

[OpenStack Infra (hudson-openstack)]

Change abandoned by venkata anil (<email address hidden>) on branch: master
Review: https://review.openstack.org/269212

[Armando Migliaccio (armando-migliaccio)]

This bug is > 180 days without activity. We are unsetting assignee and milestone and setting status to Incomplete in order to allow its expiry in 60 days.

If the bug is still valid, then update the bug status.

[Launchpad Janitor (janitor)]

[Expired for neutron because there has been no activity for 60 days.]