improve logging for downloading of layers
improve logging for downloading of layers

cvmfs/cvmfs,DrDaveD/cvmfs,DrDaveD/cvmfs,DrDaveD/cvmfs,DrDaveD/cvmfs,DrDaveD/cvmfs,cvmfs/cvmfs,cvmfs/cvmfs,DrDaveD/cvmfs,cvmfs/cvmfs,DrDaveD/cvmfs,cvmfs/cvmfs,cvmfs/cvmfs,cvmfs/cvmfs