Add rug-ctl router rebuild command

Add a command to forcibly rebuild a router. It works by destroying the
instance and building a new one, which is brute-force, but easy to
understand.

I also changed the worker's lookup for tenant router managers so the tenant
id is normalized cleanly to avoid confusion since some events use '-' and
some do not (yay, consistent!).

Change-Id: I79a622b0c6cc23041da55ec2f54f79ccf463379e