Snow coverage should not be zero the time step the snowpack melts

[jhamman]

In these lines in solve_snow.c:

    /*** NOTE *coverage should not be zero the time step the snowpack melts - FIX THIS ***/
snow->density = 0.;
snow->depth = 0.;
snow->surf_water = 0;
snow->pack_water = 0;
snow->surf_temp = 0;
snow->pack_temp = 0;
snow->coverage = 0;
snow->snow_distrib_slope = 0;
snow->store_snow = TRUE;
snow->MELTING = FALSE;