Revert "Check channel closed state in /events loop"

This reverts commit 854029e32bb43b5aeb90d5651937ecfda9ceaf57.
Check channel closed state in /events loop

When listener channel is closed, it becomes always available for
reading: select becomes an active loop which writes default-constructed
events (i.e: empty strings).

Fixes #5766.

Docker-DCO-1.1-Signed-off-by: Arnaud Porterie
<arnaud.porterie@gmail.com> (github: icecrime)