Use const DofObject* in parallel ghost sync
Use const DofObject* in parallel ghost sync

We might be iterating over a const mesh here

dschwen/libmesh,dschwen/libmesh,dschwen/libmesh,dschwen/libmesh,libMesh/libmesh,libMesh/libmesh,libMesh/libmesh,jwpeterson/libmesh,jwpeterson/libmesh,libMesh/libmesh,jwpeterson/libmesh,libMesh/libmesh,dschwen/libmesh,dschwen/libmesh,libMesh/libmesh,libMesh/libmesh,jwpeterson/libmesh,dschwen/libmesh,jwpeterson/libmesh,jwpeterson/libmesh,jwpeterson/libmesh,dschwen/libmesh,jwpeterson/libmesh,libMesh/libmesh