[Serusers] another cancel test

[Juha Heinanen]

andres,

i made another simpler cancel test.  first sip:jh at test.fi invites
sip:gs at test.fi, and gs starts ringing.  then jh sends cancel to r-uri
sip:gs at test.fi, which ser.cfg immediately at the start of the script
t_relay()s out, i.e., without doing anything to the request.  the result
is that ser correctly sends a cancel to the ip address/port of gs.

my conclusion of this is that cancels don't need to be processed by
ser.cfg, just relayed out.  perhaps others familiar with tm mystics can
confirm or deny this.

-- juha