Fix URN and available handling in gcf rpsecs.
Fix URN and available handling in gcf rpsecs.

The resource URN is now returned by the gcf-am, so the string
manipulation that was constructing a URN is no longer necessary. The
handling of the available tag was broken, always returning true. Fixed
that to pull the value out of the xml and use what the advertisement
says.

plantigrade/geni-tools,GENI-NSF/gram,tcmitchell/geni-tools,tcmitchell/geni-tools,ahelsing/geni-tools,GENI-NSF/gram,GENI-NSF/gram,plantigrade/geni-tools,ahelsing/geni-tools