Pause optional ai-rem update jobs during backup snapshots

tests/test_backup.py

@@ -821,7 +821,13 @@ else: raise SystemExit('Unexpected Docker command')
             f.write(f'EXTRA_PATHS=("{old_extra}")\n')
         package=self.build_package()
         self.env['TEST_METADATA_ONLY']='true'
-        for attempt in range(2):
+        for attempt in range(3):
+            if attempt == 1:
+                optional=['ai-rem-managed-update.timer','ai-rem-managed-update.service']
+                state=json.loads(self.state.read_text())
+                for unit in optional: state['services'][unit]='active'
+                self.state.write_text(json.dumps(state))
+                units=optional+units
             self.events.write_text('')
             result=subprocess.run(['bash',str(package),'--foreground','--enable-ai-rem'],
                                   env=self.env,capture_output=True,text=True,timeout=120)
@@ -834,6 +840,8 @@ else: raise SystemExit('Unexpected Docker command')
             self.assertEqual([(a['label'],a['source']) for a in extra],
                              [('extra-0',str(old_extra)),('extra-1','/srv/ai-rem'),('extra-2','/etc/ai-rem')])
             events=self.events.read_text()
+            if attempt == 0:
+                self.assertNotIn('systemctl stop ai-rem-managed-update.',events)
             for unit in units:
                 self.assertEqual(events.count('systemctl stop '+unit+' '),1)
                 self.assertLess(events.index('systemctl stop '+unit+' '),events.index('mariadb-dump'))