In the multicast router code don't allocate a rt timer queue for each

In the multicast router code don't allocate a rt timer queue for each
rdomain. The rttimer API is rtable/rdomain aware and so there is no need
to have so many queues.
Also init the two queues (one for IPv4 and one for IPv6) early on. This
will allow the rttable code to become simpler.
OK bluhm@