TESTS: Rename test_idle_timeout()
As this test is related to the client_idle_timeout, let's rename it
accordingly.
Resolves:
https://pagure.io/SSSD/sssd/issue/3633
Signed-off-by: Fabiano FidĂȘncio <fidencio@redhat.com>
Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>