tools: Replace oVirt logger with slf4j as frontend in engine-config

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

Change-Id: I1aeac803a58fc74919c88ac8c7ac4e3084747ce9
Bug-Url: https://bugzilla.redhat.com/1109871
Signed-off-by: Martin Perina <mperina@redhat.com>