[P3 BUG]: Redirected CSW URL contains original default CSW in xlinks

We're using /catalogue/v1/csw for the CSW URL, but when you do a GetCapabilities request the internal xlink:href URLs point at the default /geonetwork/srv/eng/csw URL. This should be fixable with the nginx subs_filter module. 

I've marked it as P3 for the moment as it's not a functional blocker