Revert "Do not start conntrack worker thread from __init__"
Revert "Do not start conntrack worker thread from __init__"

This reverts commit 4c8b97eca32c9c2beadf95fef14ed5b7d8981c5a.

After further testing it was found this did not fix the issue.

Change-Id: Ib9c4ac25752d2f68973c3615111f9f14b152d340

openstack/neutron,noironetworks/neutron,openstack/neutron,noironetworks/neutron,mahak/neutron,huntxu/neutron,huntxu/neutron,mahak/neutron,openstack/neutron,mahak/neutron