Minimum temperature limit creates issues for E3SM in aquaplanet mode

[whannah1]

I ran into this problem while trying to develop an RCE compset for E3SM. The valid temperature range for RRTMGP goes down to 180K, but for whatever reason when running in aqua planet the upper levels routinely see temperatures down to 150K.

For the time being I've enabled temperature clipping, but I'm not sure what the effect will be. It seems like a good idea to expand the look up tables to support these conditions.