ioloop: Fixed segfault crash in io_loop_call_pending(). When a callback called io_set_pending(), the io_loop_call_pending() loop crossed the end of the ioloop->io_files list.
ioloop: Fixed segfault crash in io_loop_call_pending().
When a callback called io_set_pending(), the io_loop_call_pending() loop
crossed the end of the ioloop->io_files list.

Based on patch by Stephan Bosch

LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot