tipc: Eliminate obsolete filter for unexpected unicast messages

Removes a test that ensures unicast link endpoints discard an incoming
message if it will not be consumed by the node itself and cannot be
forwarded to another node, since the preceding test already ensures that
the message is destined for this node and single-cluster TIPC no longer
performs message forwarding.

Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>