azure: Ignore tar errors
    
    Sometimes tar fails on changed in process files:
    ```
    [2021-09-07 11:03:33] + tar --ignore-failed-read -czf ipaserver_install_logs.tar.gz --warning=no-failed-read /var/log/dirsrv /var/log/httpd2 /var/log/ipa /var/log/ipaclient-install.log /var/log/ipa-custodia.audit.log /var/log/ipaserver-install.log /var/log/krb5kdc.log /var/log/pki /var/log/samba /var/lib/bind/data systemd_journal.log
    [2021-09-07 11:03:33] tar: Removing leading `/' from member names
    [2021-09-07 11:03:33] tar: Removing leading `/' from hard link targets
    [2021-09-07 11:03:33] tar: /var/log/dirsrv/slapd-IPA-TEST/access: file changed as we read it
    [2021-09-07 11:03:33] + tests_result=1
    ```
    
    This is expected failure since processes are not stopped during logs
    collection and can flush their logs.
    
    Fixes: https://pagure.io/freeipa/issue/8983
    Signed-off-by: Stanislav Levin <slev@altlinux.org>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>