Update connections-default.xml

this is a list of csw servers based on geonetwork, i discovered them a couple of months back, some of them might not be online anymore, i wanted to write a script to check that automatically. and promote them in the list based on % availability, from my blog post: http://genuchten.blogspot.nl/2013/06/amazing-list-of-geonetworks-around-globe.html