better handling of initialization of last byte

In vtkBitArray. Unused bits of last byte need to be set w.r.t
NumberOfValues instead of Size.
Status Job ID Name Coverage
  External
passed cdash-buildbot

passed ghostflow-branch-check-master

failed vtk@master-adora-linux-shared-release+cuda+gcc+mpi+optix+python2+tbb+vtkm

00:00:14

failed vtk@master-bigmac-osx-shared-debug+adios2+clang+python2+vtkm

00:26:37

failed vtk@master-duma-linux-shared-release+osmesa+ospray

00:24:46

failed vtk@master-eeloo-linux-shared-release+adios2+extdeps+java+mpi+python3+qt+tbb+vtkm

00:25:45

running vtk@master-eeloo-linux-shared-release+mpi+nogl

784:15:26

failed vtk@master-luigi-linux-shared-release+mpi+python2+tbb

00:00:32

failed vtk@master-mun-windows-shared-release+kits+mpi+python3+qt+tbb

00:55:49

failed vtk@master-mun-windows-shared-release+mpi+python3+tbb+vtkm

00:24:14

failed vtk@master-mun-windows-static-release+mpi+qt+tbb

00:55:20

failed vtk@master-taanab-linux-shared-release+adios2+mpi+python2

00:24:57

failed vtk@master-trey-osx-shared-release+python3+qt

00:58:26