fsmonitor: fix hashmap memory leak in fsmonitor_run_daemon

The `state.cookies` hashmap is initialized during daemon startup but
never freed during cleanup in the `done:` label of
fsmonitor_run_daemon().  Add a hashmap_clear() call to prevent this
memory leak.

Signed-off-by: Paul Tarjan <github@paulisageek.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/fsmonitor--daemon.c

@@ -1404,6 +1404,7 @@ static int fsmonitor_run_daemon(void)
 done:
 	pthread_cond_destroy(&state.cookies_cond);
 	pthread_mutex_destroy(&state.main_lock);
+	hashmap_clear(&state.cookies);
 	fsm_listen__dtor(&state);
 	fsm_health__dtor(&state);