Use the oVirt REST API to find out the guest IP address

This replaces the old nmap broadcast/arp hack which was
previously used to find out the guest IP address and also
allows the vagrant-ovirt plugin to be used from different
network subnets.

Requires https://github.com/fog/fog/pull/3162 and a box
image which contains the package 'ovirt-guest-agent'

I've added a dependency on fog version 1.24.0. This version
is not released yet, but I expect it to be the first future version
of fog which contains the required change. Feel free to wait
with approving this PR until the fog PR is accepted and a new
fog version has been released