core: scheduling: fixups

- Remove unused method
- List.contains() was comparing VDS and Guid wrongfully

Change-Id: I9b645459ecdca96bf19fccadab551be7f4b00f3f
Bug-Url: https://bugzilla.redhat.com/1007282
Signed-off-by: Gilad Chaplik <gchaplik@redhat.com>