machined: Don't insist on 0:0 for the state directory

We now support running machined unprivileged, so don't pass in 0:0
as the uid/gid unconditionally but just use the UID/GID we're running
as.

src/machine/machine.c

@@ -176,7 +176,7 @@ int machine_save(Machine *m) {
                         return log_oom();
         }
 
-        r = mkdir_safe_label(m->manager->state_dir, 0755, 0, 0, MKDIR_WARN_MODE);
+        r = mkdir_safe_label(m->manager->state_dir, 0755, UID_INVALID, GID_INVALID, MKDIR_WARN_MODE);
         if (r < 0)
                 return log_error_errno(r, "Failed to create '%s': %m", m->manager->state_dir);