Deinitialize plugins in the reverse plugin_type_initialization_order

Old code worked because plugin locking guaranteed that
encryption plugin is deinitialized last.
But compiled-in plugins are never locked.

This fixes encryption failures on fulltest builder

sql/sql_plugin.cc

@@ -1252,7 +1252,7 @@ static void plugin_del(struct st_plugin_int *plugin)
 
 static void reap_plugins(void)
 {
-  uint count, idx;
+  uint count;
   struct st_plugin_int *plugin, **reap, **list;
 
   mysql_mutex_assert_owner(&LOCK_plugin);
@@ -1265,9 +1265,12 @@ static void reap_plugins(void)
   reap= (struct st_plugin_int **)my_alloca(sizeof(plugin)*(count+1));
   *(reap++)= NULL;
 
-  for (idx= 0; idx < count; idx++)
+  for (uint i=0; i < MYSQL_MAX_PLUGIN_TYPE_NUM; i++)
   {
-    plugin= *dynamic_element(&plugin_array, idx, struct st_plugin_int **);
+    HASH *hash= plugin_hash + plugin_type_initialization_order[i];
+    for (uint j= 0; j < hash->records; j++)
+    {
+      plugin= (struct st_plugin_int *) my_hash_element(hash, j);
       if (plugin->state == PLUGIN_IS_DELETED && !plugin->ref_count)
       {
         /* change the status flag to prevent reaping by another thread */
@@ -1275,6 +1278,7 @@ static void reap_plugins(void)
         *(reap++)= plugin;
       }
     }
+  }
 
   mysql_mutex_unlock(&LOCK_plugin);
 
@@ -3359,9 +3363,9 @@ bool sys_var_pluginvar::session_is_default(THD *thd)
     }
   case PLUGIN_VAR_DOUBLE:
     return getopt_ulonglong2double(option.def_value) == *(double*)value;
-  default:
-    DBUG_ASSERT(0);
   }
+  DBUG_ASSERT(0);
+  return 0;
 }