Skip lbaas table creation if tables already exist

This patch makes possible upgrade from Grizzly to Icehouse
in case LoadBalancer service plugin was used in Grizzly. LoadBalancer
tables were introduced in Grizzly therefore they necessarily don't
need to be created for Havana and beyond.

This patch goes to Icehouse stable branch only because of all migration
scripts till Havana were squashed together in Juno release. That means
modified file in this patch no longer exists in current master branch.

Change-Id: I09ed3e4b142ccde44cf2e92184d0d92d898a0284
Closes-bug: 1273355
Cisco N1kv: Remove vmnetwork delete REST call on last port delete

Remove the check for last port delete and subseqeuent call to delete
the vm network. This check was moved to VSM to prevent a race
condition and ensure that the vm network is deleted from the
database when the port count becomes 0.

Change-Id: I6c08a099adfce2fdba8eefec6aadeb68a780ac37
Closes-Bug: 1373547
(cherry picked from commit 4e1c4cbcd71833095534bea9ff7617c582c300d2)
Merge "Cisco N1kv: Remove vmnetwork delete REST call on last port delete" into stable/icehouse
Merge "Skip lbaas table creation if tables already exist" into stable/icehouse