tipc: Optimization to multicast name lookup algorithm

This patch simplifies and speeds up TIPC's algorithm for identifying
on-node and off-node destinations that overlap a multicast name
sequence range.  Rather than traversing the list of all known name
publications within the cluster, it now traverses the (potentially
much shorter) list of name publications made by the node itself, and
determines if any off-node destinations exist by comparing the sizes
of the two lists.  (Since the node list must be a subset of the
cluster list, a difference in sizes means that at least one off-node
destination must exist.)

Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>