core: lock correct volume when creating a template

When creating a template out of a vm, CreateImageTemplateCommand is
being called for each of the needed vm disks. In that command there all the
disk snapshots are being loaded in order to lock the active disk
snapshot.

That logic caused for 2 bugs in that command:
1. The lock is done always on a wrong disk snapshot, as
ImagesHandler.getAllImageSnapshots() will always return the active
images as first on the list, and ImagesHandler.getActiveVolume() returns
the last on the list, the lock won't be performed on the active volume.

2. The cloned disk properties were copied from that snapshots and from
the correct snapshots, leading to wrong persisted information.

The fix is to just remove that load and set, as currently a template is
created for the active disks only we are supposed to always have the
active one already loaded.

If and when creating a template from a snapshot will be supported, the
locking could be re-inspected, right now there's no need for further db
loads.

Change-Id: I7f27535de8ec6e007035ffa7a2e5fad80460701a
Signed-off-by: Liron Aravot <laravot@redhat.com>