Remove inaccurate error message regarding ghg_input

[kkeene44]

TYPE: bug fix

KEYWORDS: ghg_input, idealized, no radiation

SOURCE: internal

DESCRIPTION OF CHANGES:
Problem:
Most idealized cases have radiation options turned off, which causes the following error message to inaccurately print to the rsl files when ideal.exe is run:

ERROR: ghg_input available only for these radiation schemes: CAM, RRTM, RRTMG, RRTMG_fast
And the LW and SW schemes must be reasonably paired together:
OK = CAM LW with CAM SW
OK = RRTM, RRTMG LW or SW, RRTMG_fast LW or SW may be mixed

Solution:
In share/module_check_a_mundo.F, add code to ensure that when radiation is turned off, not only does the message not print, but the namelist value for ghg_input is set to 0, as well.

LIST OF MODIFIED FILES:
M share/module_check_a_mundo.F

TESTS CONDUCTED:

1. Code compiles okay and no longer prints the message for idealized cases (tested with em_quarter_ss).
2. Are the Jenkins tests all passing?