Drop flat networking mode

It never worked, and is not really useful in real world anyway.

https://bugzilla.novell.com/show_bug.cgi?id=888359
Merge pull request #134 from vuntz/drop-flat

Drop flat networking mode
Revert "ha: Fix initial DB sync"

This reverts commit 962198b98e20203fe3740de8d5b46b9668864ecd.

Reverting this to implement a solution that's more aligned with how we do it
for the other services. When trying this before we simply used the wrong
command for doing the migrations.
Fix command for doing neutron db migration

The old command we used doesn't execute any migrations it just verified that
the installed migrations do not contain any branches.
NSX integration fixes
Merge pull request #135 from rhafer/db-sync

(re)fix initial db sync for HA
Merge pull request #130 from mjura/nsx-integration-fixes

NSX integration fixes