BUG/MEDIUM: stream: reset analyse_exp when analysers are stripped on error

BUG/MEDIUM: stream: reset analyse_exp when analysers are stripped on error

When the client or the server connector reports an error or a timeout that
no analyser handled, process_stream() strips all analysers from the
corresponding channel to let the error propagate, except the flt_end one.

When this happens while an analyser was yielding with the channel's
analyse_exp timer armed (e.g. an SPOE event or a Lua action waiting on an
external party), the stripped analysers can no longer manage nor reset this
timer. If it already expired, update_exp_and_leave() refuses to clear it as
long as the AN_*_FLT_END bit is kept for the two-channel filter
synchronisation, so t->expire is set to a past date, the task is requeued in
the past and process_stream() spins in a tight loop until the watchdog kills
the worker.

The request-side retry path (http_ana.c, http_req_retry) already resets
res->analyse_exp right after the same strip; do the same on both error
propagation paths of process_stream() so that an armed analyse timer can
never survive the analysers it was armed for.

This is the first commit of the series fixing github issue #3559. It must be
backported to all stable versions