nta_outgoing_tagged() kept a reference to the resolver in the tagged
request, too.

Also fixed nta_outgoing_destroy(): do not destroy the transaaction if
we have sent a final response to INVITE but we have not received ACK

darcs-hash:20070212154324-65a35-6c8698e6c6ed2950cf22b2719a3035a0033808ec.gz