Set IP address for router port correctly

When IP address is given in Add Interface operation
windown in horizon, a port is created with the IP
address, and that port is used for add_router_interface
API. With this patch, we correctly set that IP address
to the router port.

Fixes: MNA-1

Change-Id: I53ae003537dd3c40024f415a244446875a359991
Merge "Set IP address for router port correctly"