Due the to way network namespaces work, they will not survive a
container restart. This is not an issue related to Kolla or Neutron
but rather an issue with how network namespaces work.
This is putting back into place a workaround that was in correctly
removed in the past. We simply cleanup the namespace cruft when the
neutron-agents container restarts thus avoiding this issue.
Change-Id: Ic16f2f766b4fa46347ea14a1ece5a4653c69d779
Closes-Bug: #1511216
baf9d93358