systemd: always start MM after polkit service if enabling policy

Fixes https://gitlab.freedesktop.org/mobile-broadband/ModemManager/issues/113

data/Makefile.am

@@ -5,7 +5,8 @@ edit = @sed \
        -e 's|@sbindir[@]|$(sbindir)|g' \
        -e 's|@sysconfdir[@]|$(sysconfdir)|g' \
        -e 's|@localstatedir[@]|$(localstatedir)|g' \
-       -e 's|@libexecdir[@]|$(libexecdir)|g'
+       -e 's|@libexecdir[@]|$(libexecdir)|g' \
+       -e 's|@MM_POLKIT_SERVICE[@]|$(MM_POLKIT_SERVICE)|g'
 
 
 # DBus Service file

data/ModemManager.service.in

@@ -1,5 +1,7 @@
 [Unit]
 Description=Modem Manager
+After=@MM_POLKIT_SERVICE@
+Requires=@MM_POLKIT_SERVICE@
 
 [Service]
 Type=dbus