Hi Konstantin, thank you for your answer. In the meantime I managed to resolve this
problem. In moment of despair I have installed additional engine on virtual machine, the
same version as the first one. On this instance I was able to upload, download and test
connection without any issue, so I started comparing those two instances. The problem on
first instance was disabled ImageTransferProxy option. So when I ran ovirt-config -s
"ImageTransferProxyEnabled=true" followed by ovirt-engine restart, everything
start working on original instance as well.
Thank you for your answer and your time, your advice's are very good to use for
general troubleshooting procedures.
Best regards, Igor