WMS layers are double-listed in the OpenLayers layer switcher

[davidmcclure]

For some reason, WMS layers that are toggled on to the map by way of the items browser in the Neatline editor are listed twice in the OpenLayers layer switcher. The first of the two identical listings is the "real" layer (when it's checked off, the overlay disappears), and the other listing appears to be some kind of content-less duplication (checking it on and off has no apparent effect).

This doesn't appear to cause any problems from a functionality standpoint, but it's confusing and looks weird.