Fixed the bug 1352468 - UI and Horizon should take list of IPs for Tenant DNS Server IP address

Bug Description - Both Contrail UI and Horizon currently accept only a single IP address for Tenant DNS Server. Instead it should be a list of IP addresses

Change-Id: I7fb5b2292cfa68b9df1a2fc61631a0e071bec244
Merge "Fixed the bug 1352468 - UI and Horizon should take list of IPs for Tenant DNS Server IP address"