logind: never consider a closing session relevant for PK checks

https://bugzilla.redhat.com/show_bug.cgi?id=1010215

src/login/logind-dbus.c

@@ -957,6 +957,7 @@ static int have_multiple_sessions(
          * count, and non-login sessions do not count either. */
         HASHMAP_FOREACH(session, m->sessions, i)
                 if (session->class == SESSION_USER &&
+                    !session->closing &&
                     session->user->uid != uid)
                         return true;