zed: update zed.d/statechange-slot_off.sh

The statechange-slot_off.sh zedlet which was added in #15200
needed to be installed so it's included by the packages.

Additional testing has also shown that multiple retries are
often needed for the script to operate reliably.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #15210

cmd/zed/zed.d/Makefile.am

@@ -16,6 +16,7 @@ dist_zedexec_SCRIPTS = \
 	%D%/scrub_finish-notify.sh \
 	%D%/statechange-led.sh \
 	%D%/statechange-notify.sh \
+	%D%/statechange-slot_off.sh \
 	%D%/trim_finish-notify.sh \
 	%D%/vdev_attach-led.sh \
 	%D%/vdev_clear-led.sh
@@ -35,6 +36,7 @@ zedconfdefaults = \
 	scrub_finish-notify.sh \
 	statechange-led.sh \
 	statechange-notify.sh \
+	statechange-slot_off.sh \
 	vdev_attach-led.sh \
 	vdev_clear-led.sh