* check_session.c: added yet another test case for re-INVITE glare

  S2_CASE("2.6.5", "Re-INVITE glare and 500 Retry-After",
         "NUA receives re-INVITE, replies with 200, "
         "sends re-INVITE, gets 500, gets ACK, retrys INVITE,"
         "sends BYE.");

test case for SFSIP-135 and SFSIP-137



git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@13063 d0543943-73ff-0310-b7d9-9358b9ac24b2