Fix memory leak when freeing socket_table in KIST.

changes/bug23774

@@ -0,0 +1,4 @@
+  o Minor bugfixes (memory leak):
+    - Fix a minor memory-leak-at-exit in the KIST scheduler. This
+      bug should have no user-visible impact. Fixes bug 23774;
+      bugfix on 0.3.2.1-alpha.

src/or/scheduler_kist.c

@@ -158,6 +158,7 @@ static void
 free_all_socket_info(void)
 {
   HT_FOREACH_FN(socket_table_s, &socket_table, free_socket_info_by_ent, NULL);
+  HT_CLEAR(socket_table_s, &socket_table);
 }
 
 static socket_table_ent_t *