remote-viewer: Prefer ca-cert from display instead of proxy
Since oVirt engine version 220.127.116.11, the API returns certificate data for
display connection in the VM XML, so users do not need to specify it
from the command line anymore. The certificate obtained from the XML
gets precedence over the one from the command line, which is still kept
to keep compatibility of older versions of oVirt.
Signed-off-by: Eduardo Lima (Etrunko) <email@example.com>