Drop xinetd for SLE 15, leap 15 and TW

[rwx788]

xinetd was dropped and should not be scheduled for leap 15, sle 15 and
TW. See poo#32674.

[2018-03-13T10:04:54.0268 CET] [debug] scheduling boot_to_desktop tests/boot/boot_to_desktop.pm
[2018-03-13T10:04:54.0272 CET] [debug] scheduling consoletest_setup tests/console/consoletest_setup.pm
[2018-03-13T10:04:54.0272 CET] [debug] scheduling hostname tests/console/hostname.pm
[2018-03-13T10:04:54.0273 CET] [debug] scheduling zypper_lr tests/console/zypper_lr.pm
[2018-03-13T10:04:54.0274 CET] [debug] scheduling zypper_ref tests/console/zypper_ref.pm
[2018-03-13T10:04:54.0276 CET] [debug] scheduling yast2_proxy tests/console/yast2_proxy.pm
[2018-03-13T10:04:54.0277 CET] [debug] scheduling yast2_ntpclient tests/console/yast2_ntpclient.pm
[2018-03-13T10:04:54.0280 CET] [debug] scheduling yast2_tftp tests/console/yast2_tftp.pm
[2018-03-13T10:04:54.0285 CET] [debug] scheduling yast2_vnc tests/console/yast2_vnc.pm
[2018-03-13T10:04:54.0290 CET] [debug] scheduling yast2_samba tests/console/yast2_samba.pm
[2018-03-13T10:04:54.0298 CET] [debug] scheduling yast2_apparmor tests/console/yast2_apparmor.pm
[2018-03-13T10:04:54.0303 CET] [debug] scheduling yast2_lan_hostname tests/console/yast2_lan_hostname.pm
[2018-03-13T10:04:54.0308 CET] [debug] scheduling yast2_nis tests/console/yast2_nis.pm
[2018-03-13T10:04:54.0312 CET] [debug] scheduling yast2_dns_server tests/console/yast2_dns_server.pm
[2018-03-13T10:04:54.0354 CET] [debug] scheduling yast2_nfs_client tests/console/yast2_nfs_client.pm
[2018-03-13T10:04:54.0368 CET] [debug] scheduling yast2_http tests/console/yast2_http.pm
[2018-03-13T10:04:54.0372 CET] [debug] scheduling yast2_ftp tests/console/yast2_ftp.pm
[2018-03-13T10:04:54.0373 CET] [debug] scheduling consoletest_finish tests/console/consoletest_finish.pm
[2018-03-13T10:04:54.0373 CET] [debug] Early exit has been requested with _EXIT_AFTER_SCHEDULE. Only evaluating test schedule.