Fixed _reset_lists_of_nodes_cells.
Fixed _reset_lists_of_nodes_cells.

Fixed an issue in _reset_lists_of_nodes_cells where core cells were not
being set properly.

RondaStrauch/landlab,ManuSchmi88/landlab,SiccarPoint/landlab,laijingtao/landlab,Carralex/landlab,amandersillinois/landlab,landlab/landlab,SiccarPoint/landlab,cmshobe/landlab,csherwood-usgs/landlab,ManuSchmi88/landlab,landlab/landlab,cmshobe/landlab,amandersillinois/landlab,RondaStrauch/landlab,landlab/landlab,RondaStrauch/landlab,laijingtao/landlab,Carralex/landlab,Carralex/landlab,csherwood-usgs/landlab,cmshobe/landlab,ManuSchmi88/landlab