MDEV-5309 - RENAME TABLE does not check for existence of the table's engine

fix the test case for ps-protocol

mysql-test/r/plugin.result

@@ -327,6 +327,9 @@ plugin_name
 #
 INSTALL PLUGIN example SONAME 'ha_example';
 CREATE TABLE t1(a INT) ENGINE=EXAMPLE;
+SELECT * FROM t1;
+a
+FLUSH TABLES;
 UNINSTALL PLUGIN example;
 RENAME TABLE t1 TO t2;
 ERROR 42S02: Table 'test.t1' doesn't exist

mysql-test/t/plugin.test

@@ -259,6 +259,8 @@ select plugin_name from information_schema.plugins where plugin_library like 'ha
 --echo #
 INSTALL PLUGIN example SONAME 'ha_example';
 CREATE TABLE t1(a INT) ENGINE=EXAMPLE;
+SELECT * FROM t1;
+FLUSH TABLES;
 UNINSTALL PLUGIN example;
 --error ER_NO_SUCH_TABLE
 RENAME TABLE t1 TO t2;