Update cert_util.py copyright.
Update cert_util.py copyright.

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