LP #1626559: Test main.audit_log_default_db is unstable

**Reported in Launchpad by Laurynas Biveinis last update 25-05-2017 22:41:13

On PS 5.6 trunk:

main.audit_log_default_db w3 [ fail ]
Test ended at 2016-09-21 05:27:26

CURRENT_TEST: main.audit_log_default_db
Warning: Using a password on the command line interface can be insecure.
— /mnt/workspace/percona-server-5.6-trunk/BUILD_TYPE/release/Host/centos5-32/mysql-test/r/audit_log_default_db.result 2016-09-21 12:00:10.424142564 +0300
+++ /mnt/workspace/percona-server-5.6-trunk/BUILD_TYPE/release/Host/centos5-32/build/mysql-test/var/3/log/audit_log_default_db.reject 2016-09-21 12:27:25.928508108 +0300
@@ -60,6 +60,7 @@
===================================================================
"Query","<ID>","<DATETIME>","install_plugin","<CONN_ID>",0,"INSTALL PLUGIN audit_log SONAME 'audit_log.so'","root[root] @ localhost []","localhost","","",""
"Quit","<ID>","<DATETIME>","<CONN_ID>",0,"root","root","","","localhost","","test"
+"Query","<ID>","<DATETIME>","show_warnings","<CONN_ID>",0,"SHOW WARNINGS","root[root] @ localhost []","localhost","","","test"
"Query","<ID>","<DATETIME>","select","<CONN_ID>",0,"SELECT * FROM t","user1[user1] @ localhost []","localhost","","",""
"Query","<ID>","<DATETIME>","change_db","<CONN_ID>",0,"use `db1`","user1[user1] @ localhost []","localhost","","","db1"
"Change user","<ID>","<DATETIME>","<CONN_ID>",1044,"user2","user2","","","localhost","",""

mysqltest: Result content mismatch

safe_process[513]: Child process: 514, exit: 1

Server [mysqld.1 - pid: 412, winpid: 412] log:
Server log from this test:
---------SERVER LOG START----------
2016-09-21 12:27:25 413 [Note] Shutting down plugin 'audit_log'
---------SERVER LOG END------------