mfea: pim_register interfaces are always mcast capable.

This fixes error message and possibly errors as well, but
mcast routing was working even in this state, so not sure how
serious this is.  Bug was introduced earlier in the 1.5-WIP
development.

Signed-off-by: Ben Greear <greearb@candelatech.com>

xorp/fea/mfea_vif.cc

@@ -112,7 +112,7 @@ MfeaVif::start(string& error_msg)
 	return XORP_OK;
     }
 
-    if (!is_multicast_capable()) {
+    if (!(is_pim_register() || is_multicast_capable())) {
 	wants_to_be_started = true;
 	XLOG_WARNING("WARNING:  Delaying start of mfea-vif: %s because underlying vif is not multicast capable.",
 		     name().c_str());