Change ZEVENT_POOL_GUID to ZEVENT_POOL to display pool names

Outgoing mails for ZFS pool events include the pool GUID,
but not the actual pool name. Let's change this for better
readability, as it is already done in the mails for finished
pool resilvers.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by Richard Yao <richard.yao@alumni.stonybrook.edu>
Signed-off-by: Marcel Menzel <mail@mcl.gg>
Closes openzfs#14272

cmd/zed/zed.d/statechange-notify.sh

@@ -37,7 +37,7 @@ if [ "${ZEVENT_VDEV_STATE_STR}" != "FAULTED" ] \
 fi
 
 umask 077
-note_subject="ZFS device fault for pool ${ZEVENT_POOL_GUID} on $(hostname)"
+note_subject="ZFS device fault for pool ${ZEVENT_POOL} on $(hostname)"
 note_pathname="$(mktemp)"
 {
     if [ "${ZEVENT_VDEV_STATE_STR}" = "FAULTED" ] ; then
@@ -65,7 +65,7 @@ note_pathname="$(mktemp)"
     [ -n "${ZEVENT_VDEV_GUID}" ] && echo "  vguid: ${ZEVENT_VDEV_GUID}"
     [ -n "${ZEVENT_VDEV_DEVID}" ] && echo "  devid: ${ZEVENT_VDEV_DEVID}"
 
-    echo "   pool: ${ZEVENT_POOL_GUID}"
+    echo "   pool: ${ZEVENT_POOL} (${ZEVENT_POOL_GUID})"
 
 } > "${note_pathname}"