Bug#14840488 VALGRIND ERRORS IN MYSQL_CLIENT_TEST

Add missing DBUG_RETURNs, otherwise the debug-stack gets messed up,
and _db_enter_ and _db_exit_ will access data outside the current stack frame.

libmysql/libmysql.c

@@ -4653,7 +4653,7 @@ int STDCALL mysql_stmt_fetch_column(MYSQL_STMT *stmt, MYSQL_BIND *my_bind,
   if ((int) stmt->state < (int) MYSQL_STMT_FETCH_DONE)
   {
     set_stmt_error(stmt, CR_NO_DATA, unknown_sqlstate, NULL);
-    return 1;
+    DBUG_RETURN(1);
   }
   if (column >= stmt->field_count)
   {

tests/mysql_client_test.c

@@ -15278,6 +15278,7 @@ static void test_bug27876()
 
   rc= mysql_query(mysql, "set names default");
   myquery(rc);
+  DBUG_VOID_RETURN;
 }