use max not min when computing the best score

The best score is the highest score, so this was
a 'thinko'. However this bug manifests itself only
if there is more than 2 hosts in the setup.

Change-Id: I0c265aa60611793b1cd4738ec057e9e7d02747a1
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1093366
Signed-off-by: Jiri Moskovcak <jmoskovc@redhat.com>