core: scheduling: avoid running external filters in CDA

External code is user responsibility, so for the sake of performance,
avoiding running external plugins in CanDoAction.

Bug-Url: https://bugzilla.redhat.com/1014698
Change-Id: I319ca2a5d9dbbc6634639e7b842beac1cf6c6ad9
Signed-off-by: Gilad Chaplik <gchaplik@redhat.com>