tipc: Update "previous node" indicators when node address changes

This patch ensures that the "previous node" field in any existing
TIPC port message header templates is updated properly when a TIPC
network address is assigned to the node.  (Previously, only the
"originating node" field was updated.)

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