Fix "pthread_mutex_destroy on mutex with waiters!"

--- conf.c.orig	Fri Oct 19 21:40:14 2012
+++ conf.c	Tue Oct 23 22:32:14 2012
@@ -72,6 +72,7 @@ conf_free (void) {
     }
     conf_items = NULL;
     changed = 0;
+    mutex_unlock (mutex);
     mutex_free (mutex);
     mutex = 0;
 }
