add tryAddMount

we try to add a mount. if it fails, it will revert to the previous mount config.

there was a plan to make this work based on systemd-mount but we hit this bug - https://bugzilla.redhat.com/show_bug.cgi?id=1708996

src/scripts/addmount.sh

@@ -23,9 +23,11 @@ mount_file_contents="$1"
 where=$(echo "${mount_file_contents}" | grep "^Where=" | cut -d'=' -f 2)
 
 mount_filename=$(systemd-escape -p --suffix=mount "$where")
-
-echo "$mount_file_contents" > "/etc/systemd/system/${mount_filename}"
+mount_file="/etc/systemd/system/${mount_filename}"
 
 systemctl stop "${mount_filename}" || true
+
+echo "$mount_file_contents" > "${mount_file}"
+
 systemctl daemon-reload
 systemctl enable --no-block --now "${mount_filename}" || true