iotests: give tempdir an identifying name

iotests: give tempdir an identifying name

If something goes wrong causing the iotests not to cleanup their
temporary directory, it is useful if the dir had an identifying
name to show what is to blame.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-ID: <20240205155158.1843304-1-berrange@redhat.com>
Revieved-by: Michael Tokarev <mjt@tls.msk.ru>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 7d2faf0ce2ccc896ac56bc5ed2cdf4a55056a8bb)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>