Description of problem:
edit-node currently expects the filename of the original iso file to follow NVRA naming scheme, but it's not always the cased.
edit-node should have a fallback mechanism if the detection of NVRA (and buiölding the new iso name) fails.

The error looks like (with e.g. rhevh.iso):

Traceback (most recent call last):
File "./git/ovirt-node/tools/edit-node", line 1637, in <module>
  sys.exit(main())
File "./git/ovirt-node/tools/edit-node", line 1526, in main
  finished_iso = build_isoname_for_plugins(edited_iso, [n])
File "./git/ovirt-node/tools/edit-node", line 1614, in build_isoname_for_plugins
  nvra = isoname_to_nvr(editname_prefix)
File "./git/ovirt-node/tools/edit-node", line 1584, in isoname_to_nvr
  return filename_to_nvra(newfn)
File "./git/ovirt-node/tools/edit-node", line 1565, in filename_to_nvra
  v = nvra_.pop()
IndexError: pop from empty list