BUG/MEDIUM: stconn: Don't report abort from SC if read0 was already received

BUG/MEDIUM: stconn: Don't report abort from SC if read0 was already received

SC_FL_ABRT_DONE flag should never be set when SC_FL_EOS was already
set. These both flags were introduced to replace the old CF_SHUTR and to
have a flag for shuts driven by the stream and a flag for the read0 received
by the mux. So both flags must not be seen at same time on a SC. It is
espeically important because some processing are performed when these flags
are set. And wrong decisions may be made.

This patch must be backproted as far as 2.8.