tools: Replace log4j with slf4j as frontend in notifier

Replaces log4j with slf4j as logging frontend in classes which are used
in notifier.

Change-Id: Ibc192c7f10d7f9a124d2899118f6c5c7126b7230
Bug-Url: https://bugzilla.redhat.com/1109871
Signed-off-by: Martin Perina <mperina@redhat.com>