fixes #8357 - Set fog gem to version 1.25

Version 1.25, with fixes to redmine issues: 
[Refactor libvirt reset method](http://projects.theforeman.org/issues/8356)
[Cannot select vSphere clusters in folders (foreman-vmware)](http://projects.theforeman.org/issues/5855)
[Better VMWare support for non-clusters setup](http://projects.theforeman.org/issues/1945)
[Unknown region: "eu-central-1"](http://projects.theforeman.org/issues/8429)