There are tons of useless warnings about missing files on collecting
logs, such as:
```
tar: /var/log/ipaserver-kra-install.log: Warning: Cannot stat: No such file or directory
tar: /var/log/ipaepn.log: Warning: Cannot stat: No such file or directory
tar: /etc/NetworkManager/NetworkManager.conf: Warning: Cannot stat: No such file or directory
tar: /var/log/ipabackup.log: Warning: Cannot stat: No such file or directory
tar: /var/log/iparestore.log: Warning: Cannot stat: No such file or directory
...
```
Since `--ignore-failed-read` option is passed to tar the caller
doesn't care about not readable(mostly missing) files and these warnings
may be filtered out.
This improves the readability of test logs.
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>
Stanislav Levin
afef09ccba