core:VM pool snapshot should not be stateless.

After upgrading from version 3.0, the snapshots of VMs that are
part of a pool are marked as stateless although they aren't.

The proposed fix is to add a new script which fixes the already upgraded VMs.

Change-Id: I9aaccd3c624c2ab6bcc6f4a0510b26d37f2c1eee
Bug-Url: https://bugzilla.redhat.com/882621
Signed-off-by: Maor Lipchuk <mlipchuk@redhat.com>