core: migrate the LoggedUtils into slf4j

Keeping some backward compatibility within VdcCommandBase,
IrsBrokerCommand.

Bug-Url: https://bugzilla.redhat.com/1109871
Change-Id: I3e17eeb0670c456a39f354e766a771e69d160002
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>