use lookup_srv() for processing --msrp-relay option

darcs-hash:20081128110420-b2873-4953fa3b93622843bef6d02356214bbf95ead7f4
fixed: -r did sip lookup instead of msrp

darcs-hash:20081128111020-b2873-a62cf6b803de30a8b97fea0b72e6935586661c56