Clean up get_services caching.
Clean up get_services caching.

Add some comments, use a constant for the cache tag, etc.

tcmitchell/geni-portal,tcmitchell/geni-portal,charliemeyer/geni-portal,charliemeyer/geni-portal,charliemeyer/geni-portal,tcmitchell/geni-portal,tcmitchell/geni-portal,charliemeyer/geni-portal,tcmitchell/geni-portal,charliemeyer/geni-portal