Description of problem:
Currently Engine's way of determining if a Node shall be updated or not is solely based on the iso name.
As this doesn't meet all the requirements the logic needs to be updated to handle the presence of ISOs for different Engine minor releases sanely - mainly preventing Engine from suggesting upgrades from a higher to a lower minor version.

A new metadata file is going to be delivered with Node rpms. The file includes the oVirt/vdsm and Fedora/CentOS version informations which can be used to come up with better upgrade suggestions and prevent the situation where a downgrade is suggested to the user.