engine: Fix the description of two weight PolicyUnits

The description of Power Saving Weight policy unit and
Even Distribution Weight policy unit was wrong.

Change-Id: I2cbf1b4e1b959637293f45a4d19417f27c937bae
Bug-Url: https://bugzilla.redhat.com/1098591
Signed-off-by: Martin Sivak <msivak@redhat.com>