webadmin: Fix balloon while creating VMs from snapshots

During the creation of VMs from snapshots, the memory ballooning device
was always created even when the original VM had it disabled.

This patch fixes this by passing to the AddVmFromSnapshot command the
state of the ballooning device from the original VM.

Change-Id: I263abb8f3b170e6668e2e93b79700848bf056b57
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1152659
Signed-off-by: Vitor de Lima <vdelima@redhat.com>