When a host goes disabled, move the routers off of the l3 agent
of that host, distributing them amongst the other available L3 agents.
When a host goes enabled, rebalance the routers on the available
l3 agents, moving some to the newly enabled host.
Change-Id: I50fb3900ada74dd645ec38e1e681bd25ef951d54
Story: 2003857
Task: 26664
Depends-On: I710a698ebb31d48060903fb3966fa379b56ad190
Signed-off-by: Kevin Smith <kevin.smith@windriver.com>