This testmod is designed for ERI tests of compset-grid combinations that
set CLM's use_init_interp = .true. by default (which is done because
this is needed for compatibility with the hybrid refcase used for that
compset-grid combination). The problem with this setting is that, in the
branch portion of the ERI test, CLM dies with an error message if
use_init_interp is true:

   ERROR: Can only set use_init_interp if finidat is set

(because finidat is NOT set in a branch run).

Currently, ERI tests do a startup run for the ref1 case, so we don't
actually need the use_init_interp setting that we would normally need
for this compset-grid combination. So it's safe to simply turn off
use_init_interp for all of the cases in this ERI test.

Note that we cannot turn off use_init_interp via user_nl_clm, because
CLM_NAMELIST_OPTS takes precedence over user_nl_clm. We could append
'use_init_interp=.false.' to CLM_NAMELIST_OPTS, but that would still
leave the problem of init_interp_method: if that is set at all when
use_init_interp=.false., then we get an error during build-namelist. So
we need to remove the init_interp_method setting entirely; once we are
going to the trouble of doing that, we might as well just remove
use_init_interp, too.
