BUG/MEDIUM: mux-fcgi: Propagate flags to SE in fcgi_strm_wake_one_stream

BUG/MEDIUM: mux-fcgi: Propagate flags to SE in fcgi_strm_wake_one_stream

The commit is flagged as a bug because the same fix on the H2 multiplexer was
reported as a bug. But no issue was reported.

When a stream is explicitly woken up by the FCGI conneciton, if an error
condition is detected, the corresponding error flag is set on the SE. So
SE_FL_ERROR or SE_FL_ERR_PENDING, depending if the end of stream was
reported or not.

However, there is no attempt to propagate other termination flags. We must
be sure to properly set SE_FL_EOI and SE_FL_EOS when appropriate to be able
to switch a pending error to a fatal error.

Because of this bug, the SE could remain with a pending error and no end of
stream, preventing the applicative stream to trully abort it. It means on
some abort scenario, it seems to be possible to block a stream infinitely.

This patche depends on:

  * MEDIUM: mux-fcgi: Add a function to propagate termination flags from fstrm to SE
  * BUG/MEDIUM: mux-fcgi: Properly handle read0 on partial records

This patch could be backported at least as far as 2.8 after a period of
observation. However no bug was reportedn so there is no rush.