Modifications (in shell_commands) to enable a hybrid run for SSP compsets
(e.g., SSP370 or SSP585), starting from end of v3 historical run

Other modifications (same as for wcprod) should result in a case that has the 
same namelist settings as the water cycle production sims

Run these for at least 1 day to see all output.
Also use the CMIP6 compsets.
