tipc: Fix bugs in message error code display when debugging

This patch corrects two problems in the display of error code
information in TIPC messages when debugging:
- no longer tries to display error code in NAME_DISTRIBUTOR
  messages, which don't have the error field
- now displays error code in 24 byte data messages, which do
  have the error field

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