MW-399 Freeing wsrep_status_vars, before provider is released.

This is needed to clear THD::wsrep_status_vars reference,
which would otherwise remain to point to status variable array, which is no more effective.

sql/wsrep_var.cc

@@ -300,8 +300,15 @@ bool wsrep_provider_update (sys_var *self, THD* thd, enum_var_type type)
   if (wsrep_inited == 1)
     wsrep_deinit(false);
 
-  char* tmp= strdup(wsrep_provider); // wsrep_init() rewrites provider 
+  char* tmp= strdup(wsrep_provider); // wsrep_init() rewrites provider
                                      //when fails
+
+  /* provider status variables are allocated in provider library
+     and need to freed here, otherwise a dangling reference to
+     wsrep_status_vars would remain in THD
+  */
+  wsrep_free_status(thd);
+
   if (wsrep_init())
   {
     my_error(ER_CANT_OPEN_LIBRARY, MYF(0), tmp);