main: add log message for timeout reached with -t option

This should make it more clear why chronyd exits if -q/-Q does not
finish before the timeout is reached.

main.c

@@ -166,6 +166,8 @@ signal_cleanup(int x)
 static void
 quit_timeout(void *arg)
 {
+  LOG(LOGS_INFO, "Timeout reached");
+
   /* Return with non-zero status if the clock is not synchronised */
   exit_status = REF_GetOurStratum() >= NTP_MAX_STRATUM;
   SCH_QuitProgram();