Small cleanup of dlnd's use of glc_nec

As noted in https://github.com/ESCOMP/CDEPS/pull/364#discussion_r2635946202, I think dlnd can get glc_nec from glc_elevclass_mod. And, importantly, I think dlnd should *not* be calling glc_elevclass_init, since that should already be called by CMEPS.

This is a small cleanup, but should be tested to ensure it is bit-for-bit.

@Katetc - I'm tentatively assigning it to you, thinking it could make sense to do this along with #365 , though with the caveat that #365 will probably change answers whereas we want to ensure that this cleanup is bit-for-bit.