To find router-id, get the routers from external network, then find the correct router that matches the internal network for the floating ip. This avoids walking all ports.

Change-Id: If2fa246a6ba9eff8fbbb5262cd963fd2cca1e686
Closes-Bug: 1371368
Merge "To find router-id, get the routers from external network, then find the correct router that matches the internal network for the floating ip. This avoids walking all ports."