MINOR: mux-h1: Remove usless code inside shutr callback

For now, at the transport-layer level, there is no shutr callback (in
xprt_ops). Thus, to ease the aborts refacotring, the code is removed from
the h1_shutr() function. The callback is not removed for now. It is only
kept to have a trace message. It may be handy for debugging sessions.
1 file changed