Cisco: Set correct nullable for switch_ip, instance_id, vlan_id

Corrected the following model according to database
content:
 - NOT NULL for NexusPortBinding switch_ip and instance_id

In migrations folsom_initial was set incorrect nullable parameter:
- Set vlan_id NOT NULL in cisco_nexusport_bindings.

Partial-Bug: #1296282

Change-Id: Ie5315fcbf227025c30ab4a4b97ec2a140ee3923c
ip-lib : use "ip neigh replace" instead of "ip neigh add"

Closes bug #1311002

Change-Id: Ie50bc0bff32b7f97ac317ccc2521bbea52d59ca3
Merge "ip-lib : use "ip neigh replace" instead of "ip neigh add""
Merge "Cisco: Set correct nullable for switch_ip, instance_id, vlan_id"