tipc: Optimize re-initialization of port message header templates

Removes an unnecessary check in the logic that updates the message
header template for existing ports when a node's network address is
first assigned. There is no longer any need to check to see if the
node's network address has actually changed since the calling routine
has already verified that this is so.

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