When there is a layer group with several sub-layers, the group has a
"default" style and the sub-layers each have a "default" layer. QGIS
was showing two "default" styles for the sub-layers, which would be
confusing to the user and could pick the wrong legend for the
sub-layer if the user picked the wrong entry (the first one).
Had to create a static lib for wmsprovider in order to unittest it.
