Added functional tests for L3 schedulers.

Added functional tests for L3 schedulers.

Legacy mode agents considered.

Following test cases are added:
Common scenarios:
1. No routers scheduled if no agents are present
2. No routers scheduled if it is already hosted
3. No routers scheduled if all agents are down
4. Router scheduled to the agent if router is not yet hosted
5. Router scheduled to the agent even if it already hosts a router

Following scenario specific to least routers scheduler is added:
1. Router is scheduled to agent hosting least routers

For each of Chance and Least Router schedulers auto scheduling is also verified.

A total of 22 test cases are added.

Change-Id: Ic4df299bac83c80abf0890a81d2dd36d15993b33