tipc: Ensure network address change doesn't impact configuration service

Enhances command validation done by TIPC's configuration service so
that it works properly even if the node's network address is changed in
mid-operation. The default node address of <0.0.0> is now recognized as an
alias for "this node" even after a new network address has been assigned.

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