multipathd: reset delay_wait_checks counter on failure

multipathd: reset delay_wait_checks counter on failure

If path reinstantiation is delayed by delay_wait_checks, wait_checks
is counting down, the path fails during the delay phase, and then
comes up again, the wait_check counter starts counting down at the
same value where it previously stopped, which may be very low (even 1).

To avoid that, reset the counter to pp->delay_wait_checks if a failure
is encountered during the delay phase.

Signed-off-by: Martin Wilck <mwilck@suse.com>