tools: Replace log4j with slf4j as frontend in engine-config

Replaces log4j with slf4j as logging frontend in classes which are used
in engine-config tool.

Change-Id: Idc3d2a507f51c11b468c6af33a8f714545d3d695
Bug-Url: https://bugzilla.redhat.com/1109871
Signed-off-by: Martin Perina <mperina@redhat.com>