VTK-2649 - lock revision-buttons on restore and unlock on error (on success content is replaced). Also fix callbacks.error possibility in serverFacade.
VTK-2649 - lock revision-buttons on restore and unlock on error (on success content is replaced). Also fix callbacks.error possibility in serverFacade.

vtkio/vtk,vtkio/vtk,vtkio/vtk,vtkio/vtk,vtkio/vtk,vtkio/vtk,vtkio/vtk,vtkio/vtk