Revert "BUG/MINOR: stream-int: Don't block reads in si_update_rx() if chn may receive"

Revert "BUG/MINOR: stream-int: Don't block reads in si_update_rx() if chn may receive"

This reverts commit e0dec4b7b258101f6d5faa15234103a45c16f0f8.

At first glance, channel_is_empty() was used on purpose in si_update_rx(),
because of the HTX ("b3e0de46c" MEDIUM: stream-int: Rely only on
SI_FL_WAIT_ROOM to stop data receipt). It is not pretty clear for now why
channel_may_recv() sould not be used here but this change introduce a
possible infinite loop with the stats applet. So, it is safer to revert the
patch, waiting for a better understanding of the probelm.

This means the abortonclose option will be broken again on the 2.3 and lower
versions.

This patch should fix the issue #1360. It must be backported as far as 2.0.