Adds test for router rescheduling

Tests that routers can be unscheduled and rescheduled between L3-agents while
still maintaining connectivity to servers

Will work with l3-ha or single l3-agent as well.

Note: future patches will refactor this code to support dhcp and lbaas
rescheduling.

Change-Id: Ia5319f6ee055cc163cbf70c8f1a61745aac50ab5
2 files changed