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