Fix API version validation bug.
Fix API version validation bug.

Teach omni how to validate the user-specified API version.

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