When shuttind down, we always unconditionally try to remove the natgw address

When shuttind down, we always unconditionally try to remove the natgw address
even if we are not currently the natgw master.
This adds extra reliability in case we have stopped previously without removing it proper,
but does add spam messages to syslog everytime we shutdowm.

Remove these spam messages from pulluting the syslog upon normal shutdown