test: mask mdmonitor when building image

Follow-up for 22e31655f3.

test/test-functions

@@ -1289,6 +1289,10 @@ install_mdadm() {
     for unit in "${mdadm_units[@]}"; do
         image_install "${ROOTLIBDIR:?}/$unit"
     done
+
+    # Disable the mdmonitor service, since it fails if there's no valid email address
+    # configured in /etc/mdadm.conf, which just unnecessarily pollutes the logs
+    "${SYSTEMCTL:?}" mask --root "${initdir:?}" mdmonitor.service || :
 }
 
 install_compiled_systemd() {

test/units/testsuite-64.sh

@@ -1159,10 +1159,6 @@ testcase_mdadm_lvm() {
     helper_check_device_units
 }
 
-# Disable the mdmonitor service, since it fails if there's no valid email address
-# configured in /etc/mdadm.conf, which just unnecessarily pollutes the logs
-systemctl list-unit-files mdmonitor.service >/dev/null && systemctl mask --runtime mdmonitor.service
-
 udevadm settle
 udevadm control --log-level debug
 lsblk -a