timesync: export manager_is_connected()

This function use useful from other files, so let's export it.

src/timesync/timesyncd-manager.c

@@ -1013,7 +1013,9 @@ clear:
         return r;
 }
 
-static bool manager_is_connected(Manager *m) {
+bool manager_is_connected(Manager *m) {
+        assert(m);
+
         /* Return true when the manager is sending a request, resolving a server name, or
          * in a poll interval. */
         return m->server_socket >= 0 || m->resolve_query || m->event_timer;

src/timesync/timesyncd-manager.h

@@ -124,5 +124,6 @@ void manager_flush_server_names(Manager *m, ServerType t);
 
 int manager_connect(Manager *m);
 void manager_disconnect(Manager *m);
+bool manager_is_connected(Manager *m);
 
 int manager_setup_save_time_event(Manager *m);