SessionManager: remove comparison of request-uri with local account.id; use To header for that purpose

- this resulted in rejecting good incoming connection, because they
  have request-uri of kind "sip:qweqwe@10.1.1.3:58644"

darcs-hash:20090324071810-b2873-f81585d7521db1553b27e2e9f9dd711519f44e25