zed.d/*-notify.sh: use mktemp instead of generating temp path manually

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #11935

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

@@ -25,7 +25,7 @@ zed_rate_limit "${rate_limit_tag}" || exit 3
 
 umask 077
 note_subject="ZFS ${ZEVENT_SUBCLASS} error for ${ZEVENT_POOL} on $(hostname)"
-note_pathname="${TMPDIR:="/tmp"}/$(basename -- "$0").${ZEVENT_EID}.$$"
+note_pathname="$(mktemp)"
 {
     echo "ZFS has detected a data error:"
     echo

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

@@ -31,7 +31,7 @@ umask 077
 pool_str="${ZEVENT_POOL:+" for ${ZEVENT_POOL}"}"
 host_str=" on $(hostname)"
 note_subject="ZFS ${ZEVENT_SUBCLASS} event${pool_str}${host_str}"
-note_pathname="${TMPDIR:="/tmp"}/$(basename -- "$0").${ZEVENT_EID}.$$"
+note_pathname="$(mktemp)"
 {
     echo "ZFS has posted the following event:"
     echo

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

@@ -41,7 +41,7 @@ fi
 
 umask 077
 note_subject="ZFS ${ZEVENT_SUBCLASS} event for ${ZEVENT_POOL} on $(hostname)"
-note_pathname="${TMPDIR:="/tmp"}/$(basename -- "$0").${ZEVENT_EID}.$$"
+note_pathname="$(mktemp)"
 {
     echo "ZFS has finished a ${action}:"
     echo

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

@@ -37,7 +37,7 @@ fi
 
 umask 077
 note_subject="ZFS device fault for pool ${ZEVENT_POOL_GUID} on $(hostname)"
-note_pathname="${TMPDIR:="/tmp"}/$(basename -- "$0").${ZEVENT_EID}.$$"
+note_pathname="$(mktemp)"
 {
     if [ "${ZEVENT_VDEV_STATE_STR}" = "FAULTED" ] ; then
         echo "The number of I/O errors associated with a ZFS device exceeded"

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

@@ -19,7 +19,7 @@ zed_check_cmd "${ZPOOL}" || exit 9
 
 umask 077
 note_subject="ZFS ${ZEVENT_SUBCLASS} event for ${ZEVENT_POOL} on $(hostname)"
-note_pathname="${TMPDIR:="/tmp"}/$(basename -- "$0").${ZEVENT_EID}.$$"
+note_pathname="$(mktemp)"
 {
     echo "ZFS has finished a trim:"
     echo