tokudb.backup tests not cleaning up, fail with --repeat=2

[Laurynas Biveinis]

On 5.6 trunk, with --repeat=2:

tokudb.backup.innodb_use_native_aio_enabled w4 [ pass ] 6
tokudb.backup.innodb_use_native_aio_enabled w4 [ fail ]
...
        Test ended at 2017-02-28 18:09:46

CURRENT_TEST: tokudb.backup.innodb_use_native_aio_enabled
mysqltest: At line 9: command "mkdir" failed with error 1. my_errno=17

The result from queries just before the failure was:
SELECT @@innodb_use_native_aio;
@@innodb_use_native_aio
1

tokudb.backup.rpl_tokudb_commit_sync w4 [ pass ] 2143
tokudb.backup.rpl_tokudb_commit_sync w4 [ fail ]
        Test ended at 2017-02-28 18:09:56

CURRENT_TEST: tokudb.backup.rpl_tokudb_commit_sync
mysqltest: At line 9: command "mkdir" failed with error 1. my_errno=17

[Vlad Lesin (vlad-lesin)]

https://github.com/percona/percona-server/pull/1608
https://github.com/percona/percona-server/pull/1609

[Laurynas Biveinis (laurynas-biveinis)]

tokudb.backup.rpl_tokudb_commit_sync w4 [ pass ] 2143
tokudb.backup.rpl_tokudb_commit_sync w4 [ fail ]
        Test ended at 2017-02-28 18:09:56

CURRENT_TEST: tokudb.backup.rpl_tokudb_commit_sync
mysqltest: At line 9: command "mkdir" failed with error 1. my_errno=17

is not fixed by the above fixes.

[Laurynas Biveinis (laurynas-biveinis)]

https://jira.percona.com/browse/TDB-97

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PS-2240