core: Make sure cgroup_oom_queue is flushed on manager exit

The unit queues are not serialized/deserialized (they are recreated
after reexec/reload instead). The destroyed units are not removed from
the cgroup_oom_queue. That means the queue may contain possibly invalid
pointers to released units.

Fix this by removing the units from cgroup_oom_queue as we do for
others. When at it, sync assert checks with currently existing queues
and put them in order in the manager cleanup code.

src/core/manager.c

@@ -1437,6 +1437,10 @@ static void manager_clear_jobs_and_units(Manager *m) {
         assert(!m->cleanup_queue);
         assert(!m->gc_unit_queue);
         assert(!m->gc_job_queue);
+        assert(!m->cgroup_realize_queue);
+        assert(!m->cgroup_empty_queue);
+        assert(!m->cgroup_oom_queue);
+        assert(!m->target_deps_queue);
         assert(!m->stop_when_unneeded_queue);
         assert(!m->start_when_upheld_queue);
         assert(!m->stop_when_bound_queue);

src/core/unit.c

@@ -733,6 +733,9 @@ Unit* unit_free(Unit *u) {
         if (u->in_dbus_queue)
                 LIST_REMOVE(dbus_queue, u->manager->dbus_unit_queue, u);
 
+        if (u->in_cleanup_queue)
+                LIST_REMOVE(cleanup_queue, u->manager->cleanup_queue, u);
+
         if (u->in_gc_queue)
                 LIST_REMOVE(gc_queue, u->manager->gc_unit_queue, u);
 
@@ -742,8 +745,8 @@ Unit* unit_free(Unit *u) {
         if (u->in_cgroup_empty_queue)
                 LIST_REMOVE(cgroup_empty_queue, u->manager->cgroup_empty_queue, u);
 
-        if (u->in_cleanup_queue)
-                LIST_REMOVE(cleanup_queue, u->manager->cleanup_queue, u);
+        if (u->in_cgroup_oom_queue)
+                LIST_REMOVE(cgroup_oom_queue, u->manager->cgroup_oom_queue, u);
 
         if (u->in_target_deps_queue)
                 LIST_REMOVE(target_deps_queue, u->manager->target_deps_queue, u);