Fixes bug 1042104
The fix follows the patch that was done on the DHCP agent to enable
the user to configure the usage of namespaces. In the event that
namspaces are disabled the agent is limited to running only one
router. The agent needs to define the router_id that is supported.
The process in this case is:
1. create router
2. start agent with router id
Change-Id: I2a71dc009c5aea285ff9f903b3faa99b0c9f820f