make mtr_check to monitor mysql.plugin table too.

fix tests to clean up properly

mysql-test/include/mtr_check.sql

@@ -67,6 +67,7 @@ BEGIN
     mysql.help_keyword,
     mysql.help_relation,
     mysql.host,
+    mysql.plugin,
     mysql.proc,
     mysql.procs_priv,
     mysql.roles_mapping,

mysql-test/suite/perfschema/r/hostcache_ipv4_auth_plugin.result

@@ -197,3 +197,4 @@ REVOKE PROXY ON 'plug_dest'@'santa.claus.ipv4.example.com'
 DROP USER 'plug'@'santa.claus.ipv4.example.com';
 DROP USER 'plug_dest'@'santa.claus.ipv4.example.com';
 set global debug_dbug= default;
+delete from mysql.plugin where name='test_plugin_server';

mysql-test/suite/perfschema/r/hostcache_ipv6_auth_plugin.result

@@ -197,3 +197,4 @@ REVOKE PROXY ON 'plug_dest'@'santa.claus.ipv6.example.com'
 DROP USER 'plug'@'santa.claus.ipv6.example.com';
 DROP USER 'plug_dest'@'santa.claus.ipv6.example.com';
 set global debug_dbug= default;
+delete from mysql.plugin where name='test_plugin_server';

mysql-test/suite/perfschema/t/hostcache_ipv4_auth_plugin.test

@@ -86,4 +86,5 @@ DROP USER 'plug'@'santa.claus.ipv4.example.com';
 DROP USER 'plug_dest'@'santa.claus.ipv4.example.com';
 
 set global debug_dbug= default;
+delete from mysql.plugin where name='test_plugin_server';
 

mysql-test/suite/perfschema/t/hostcache_ipv6_auth_plugin.test

@@ -87,4 +87,5 @@ DROP USER 'plug'@'santa.claus.ipv6.example.com';
 DROP USER 'plug_dest'@'santa.claus.ipv6.example.com';
 
 set global debug_dbug= default;
+delete from mysql.plugin where name='test_plugin_server';
 

mysql-test/suite/plugins/r/audit_null_debug.result

+set @old_dbug=@@debug_dbug;
 call mtr.add_suppression("Incorrect key file for table.*mysql.plugin.MYI");
 SET debug_dbug='+d,myisam_pretend_crashed_table_on_usage';
 install plugin audit_null soname 'adt_null';
 ERROR HY000: Incorrect key file for table './mysql/plugin.MYI'; try to repair it
-SET debug_dbug='-d,myisam_pretend_crashed_table_on_usage';
+SET debug_dbug=@old_dbug;
 install plugin audit_null soname 'adt_null';
 SET debug_dbug='+d,myisam_pretend_crashed_table_on_usage';
 uninstall plugin audit_null;
 ERROR HY000: Incorrect key file for table './mysql/plugin.MYI'; try to repair it
-SET debug_dbug='-d,myisam_pretend_crashed_table_on_usage';
+SET debug_dbug=@old_dbug;
 uninstall plugin audit_null;
 ERROR 42000: PLUGIN audit_null does not exist
+delete from mysql.plugin where name='audit_null';

mysql-test/suite/plugins/t/audit_null_debug.test

@@ -5,6 +5,7 @@ if (!$ADT_NULL_SO) {
   skip No NULL_AUDIT plugin;
 }
 
+set @old_dbug=@@debug_dbug;
 call mtr.add_suppression("Incorrect key file for table.*mysql.plugin.MYI");
 
 #
@@ -15,15 +16,17 @@ SET debug_dbug='+d,myisam_pretend_crashed_table_on_usage';
 --replace_result \\ /
 --error 126
 install plugin audit_null soname 'adt_null';
-SET debug_dbug='-d,myisam_pretend_crashed_table_on_usage';
+SET debug_dbug=@old_dbug;
 
 install plugin audit_null soname 'adt_null';
 SET debug_dbug='+d,myisam_pretend_crashed_table_on_usage';
 --replace_result \\ /
 --error 126
 uninstall plugin audit_null;
-SET debug_dbug='-d,myisam_pretend_crashed_table_on_usage';
+SET debug_dbug=@old_dbug;
 
 --error 1305
 uninstall plugin audit_null;
 
+delete from mysql.plugin where name='audit_null';
+