test: mask mdmonitor when building image

Follow-up for 22e31655f3f9f54d932d4f48b92b36698e701729.

(cherry picked from commit 0f236e8cd6309cdc392d9e62bc545dcd497a9c50)
(cherry picked from commit 374a0f678817c1ab054587def008e65806f9c437)
(cherry picked from commit 74978b25bc686509c4f89ef6fa0e15453ad4362b)
(cherry picked from commit 1f392470cbbe249d5e706be59c8be799e1917d99)

test/test-functions

@@ -1209,6 +1209,10 @@ 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

@@ -988,10 +988,6 @@ testcase_mdadm_lvm() {
 
 : >/failed
 
-# 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