Fix #65.
Fix #65.

Add a "--no-tz" command line option to tell omni to avoid passing a
timezone on the RenewSliver call. This allows omni to be backward
compatible with older SFA-based aggregates like those found in the
GENI mesoscale deployment.

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