v1.10: Fix gsm2016 in diffuse_radio_sky_model()

From f785a23 (skymod):
=====================

In astroutils/catalog.py,

(*) In function diffuse_radio_sky_model(), pass explicit
initialization parameters in call to GlobalSkyModel2016() of the
PyGSM module
(*) Generate gsm2016 output initially in Rayleigh-Jeans temperature
units and then convert to flux density.