Make it possible to overwrite shr_const values in CESM

[billsacks]

This is needed for idealized test cases

NOT YET TESTED: This was a quick change, for review and testing by @gunterl

If we want to be careful about this, we should test to ensure that this doesn't change answers in CESM

[gunterl]

These changes do not seem to be working as we want.
I tried by setting the value of rhoi in the default namelist and also in user_nl_cism but the value still gets overwritten by the CESM default.

[gunterl]

Actually it works if an ifndef(CCSMCOUPLED) is removed in libglide/glide_setup.F90.
Let's test this further before moving this change to master.

[billsacks]

@Katetc - @gunterl has looked at this and it's working for him. I'm assigning it to you because it would be good to coordinate bringing this to master along with generally updating cism-wrapper to point to the latest version of master. I'd feel more comfortable if this were tested in a bit-for-bit tag, which may mean keeping this separate from other updates to master if they have any expected answer changes.