fix small memory leak at the end of umount
fix small memory leak at the end of umount

cvmfs/cvmfs,reneme/cvmfs,alhowaidi/cvmfsNDN,DrDaveD/cvmfs,reneme/cvmfs,DrDaveD/cvmfs,Gangbiao/cvmfs,Moliholy/cvmfs,trshaffer/cvmfs,cvmfs/cvmfs,cvmfs/cvmfs,DrDaveD/cvmfs,DrDaveD/cvmfs,djw8605/cvmfs,trshaffer/cvmfs,alhowaidi/cvmfsNDN,trshaffer/cvmfs,djw8605/cvmfs,Moliholy/cvmfs,alhowaidi/cvmfsNDN,DrDaveD/cvmfs,djw8605/cvmfs,Moliholy/cvmfs,Gangbiao/cvmfs,cvmfs/cvmfs,DrDaveD/cvmfs,reneme/cvmfs,trshaffer/cvmfs,Gangbiao/cvmfs,alhowaidi/cvmfsNDN,reneme/cvmfs,cvmfs/cvmfs,Moliholy/cvmfs,Moliholy/cvmfs,cvmfs/cvmfs,reneme/cvmfs,djw8605/cvmfs,Gangbiao/cvmfs,alhowaidi/cvmfsNDN,Gangbiao/cvmfs,cvmfs/cvmfs,trshaffer/cvmfs,DrDaveD/cvmfs,djw8605/cvmfs