incorrect selection of timesteps for 6hourly geopotential from AUS2200

[paolap]

AUS2200 1hourly files have some variables only every 6 hours but at 01-07 etc timesteps.
This is causing issues in properly build files for geopotential heigh which relies on one of this variables.
Somehow files are expected to have values starting at 06 to 00 of day after which throws everything off as only 07-13-19 timsteps are included. They should start at 01!!