global uniform I2000 case is finding a NaN in coupler output

The following test is crashing with an error about a NaN

SMS.f19_g17.I2000SlimRsGs.cheyenne_intel.clm-global_uniform

The output error is...

```
721: MML depth (negative) from surface of midpoint of each soil layer
721:
721:
721: MML the var we are trying is:
957:Image PC Routine Line Source
957:cesm.exe 000000000151B5AD Unknown Unknown Unknown
957:cesm.exe 0000000000C9B2E2 shr_abort_mod_mp_ 114 shr_abort_mod.F90
957:cesm.exe 00000000004F9057 abortutils_mp_end 43 abortutils.F90
957:cesm.exe 00000000004F855C lnd_import_export 419 lnd_import_export.F90
957:cesm.exe 00000000004EE6D7 lnd_comp_mct_mp_l 482 lnd_comp_mct.F90
957:cesm.exe 00000000004249E4 component_mod_mp_ 728 component_mod.F90
957:cesm.exe 000000000040A12D cime_comp_mod_mp_ 2712 cime_comp_mod.F90
957:cesm.exe 000000000042468C MAIN__ 125 cime_driver.F90
957:cesm.exe 0000000000407E1E Unknown Unknown Unknown
957:libc-2.22.so 00002B193D5046E5 __libc_start_main Unknown Unknown
957:cesm.exe 0000000000407D29 Unknown Unknown Unknown
957:MPT ERROR: Rank 957(g:957) is aborting with error code 1001.
957: Process ID: 25969, Host: r3i2n1, Program: /glade/scratch/erik/SMS.f19_g17.I2000SlimRsGs.cheyenne_intel.clm-global_uniform.GC.slim-n1_cesm21chintelasl/bld/cesm.exe
957: MPT Version: HPE MPT 2.19 02/23/19 05:30:09
```

And the line is:

` call endrun( sub//' ERROR: One or more of the output from CLM to the coupler are NaN ' )`