engine: list Ubuntu 14.04 as an operating system

Add Ubuntu 14.04 as an operating system to new/edit vms dialog.

Change-Id: I38c296b00167821b6f17352c81c5dc260e313070
Bug-Url: https://bugzilla.redhat.com/1101219
Signed-off-by: Rene Koch <rkoch@linuxland.at>
Signed-off-by: Roy Golan <rgolan@redhat.com>
Signed-off-by: Vitor de Lima <vdelima@redhat.com>