tipc: Remove obsolete manipulation of message re-route count field

Eliminates code that increments and validates the re-route count field
of payload messages, since the elimination of multi-cluster support
means that it is no longer necessary for TIPC to forward incoming messages
to another node. (The obsolete code was incorrect anyway, since it
incorrectly incremented the re-route count field of messages that
originated on the node that forwarded the message.)

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