Fix state of router when we notice it is missing

We used to rely on receiving an event to know that a router had been
deleted. We're going to be filtering that event out (see subsequent
changesets), so we need to properly detect that a router VM is gone and
mark ourselves as down so the automaton can reboot us.

Change-Id: I287a8dcc208bc709687cf63a0f17ace25265d178
Ignore POLL requests when in an error state

There is a race condition between setting a router into an error state
and receiving a poll request from the health monitor. If we do see a
poll request, ignore it and no-op the transition back to CalcAction
instead of resetting an error state that may have been set after the
poll action went into the queue.

Change-Id: Ie82d937812b79357bdcda13dd11aa3a3d732a0dc
Ignore notifications caused by RUG actions

Ignore notifications where the context user is the same as the RUG's
user, so we don't make more work for ourselves and so we can properly
handle the error loop detection without race conditions.

Change-Id: I16140ead173b7fb2caedec1b69f1271f9f99f51c