mkosi: Mask mdmonitor and isc-dhcp-server services

They always fail and do not ship with proper units so we can't
disable them with presets so we mask them instead.

Author: DaanDeMeyer

mkosi.conf

@@ -40,6 +40,9 @@ KernelCommandLine=systemd.crash_shell
                   panic=-1
                   softlockup_panic=1
                   panic_on_warn=1
+                  # These don't ship proper units with [Install] directives so we have to mask them instead.
+                  systemd.mask=isc-dhcp-server.service
+                  systemd.mask=mdmonitor.service
 
 [Host]
 Credentials=journal.storage=persistent