Instead of relying on the order, the VDAgentMonitorsConfigV2 message
contains the guest_output_id field, which identifies the output head to
which the config belongs.

Update the monitors_config algorithm to use the guest_output_id instead
of the index. Any output that does not have it's monitors_config with
it's guest_output_id in the list is disabled. The order of items in the
list no longer matters, the guest_output_id is used now.

Signed-off-by: Lukáš Hrázký <lhrazky@redhat.com>