limit number of handles in S3 uploader
limit number of handles in S3 uploader

Gangbiao/cvmfs,DrDaveD/cvmfs,Gangbiao/cvmfs,djw8605/cvmfs,djw8605/cvmfs,cvmfs/cvmfs,cvmfs/cvmfs,DrDaveD/cvmfs,Gangbiao/cvmfs,cvmfs/cvmfs,DrDaveD/cvmfs,Gangbiao/cvmfs,cvmfs/cvmfs,cvmfs/cvmfs,cvmfs/cvmfs,Gangbiao/cvmfs,DrDaveD/cvmfs,djw8605/cvmfs,djw8605/cvmfs,DrDaveD/cvmfs,DrDaveD/cvmfs,DrDaveD/cvmfs,cvmfs/cvmfs,djw8605/cvmfs