Implement "restart" for RemoteDB services

It's not really a restart, as we can't control it, but it checks the DB
and returns the status properly.

Fixes: 7cdffe7

lib/foreman_maintain/utils/service/abstract.rb

@@ -55,6 +55,10 @@ def stop
         raise NotImplementedError
       end
 
+      def restart
+        raise NotImplementedError
+      end
+
       def enable
         raise NotImplementedError
       end

lib/foreman_maintain/utils/service/remote_db.rb

@@ -38,6 +38,14 @@ def stop
         [0, db_status.last]
       end
 
+      def restart
+        command_name = ForemanMaintain.command_name
+        db_status(<<~MSG
+          Remote databases are not managed by #{command_name} and therefore was not restarted.
+        MSG
+                 )
+      end
+
       def running?
         status.first == 0
       end