Fixes deprecation warning on MacOS 10.12+ re: OSSpinLock
Fixes deprecation warning on MacOS 10.12+ re: OSSpinLock

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