better error return message (indicate when the message is from the AM). Plus better handling on error from createsliver
better error return message (indicate when the message is from the AM). Plus better handling on error from createsliver

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