added a ScopedCallback utility to safely release aquired resources
added a ScopedCallback utility to safely release aquired resources

reneme/cvmfs,alhowaidi/cvmfsNDN,Moliholy/cvmfs,cvmfs-testing/cvmfs,cvmfs-testing/cvmfs,DrDaveD/cvmfs,DrDaveD/cvmfs,bbockelm/cvmfs,ruvolof/cvmfs,reneme/cvmfs,djw8605/cvmfs,cvmfs/cvmfs,DrDaveD/cvmfs,reneme/cvmfs,alhowaidi/cvmfsNDN,DrDaveD/cvmfs,alhowaidi/cvmfsNDN,djw8605/cvmfs,bbockelm/cvmfs,ruvolof/cvmfs,ruvolof/cvmfs,cvmfs/cvmfs,MicBrain/cvmfs,cvmfs-testing/cvmfs,djw8605/cvmfs,djw8605/cvmfs,bbockelm/cvmfs,trshaffer/cvmfs,Moliholy/cvmfs,DrDaveD/cvmfs,cvmfs/cvmfs,trshaffer/cvmfs,bbockelm/cvmfs,trshaffer/cvmfs,btovar/cvmfs,reneme/cvmfs,Moliholy/cvmfs,cvmfs/cvmfs,MicBrain/cvmfs,Gangbiao/cvmfs,btovar/cvmfs,Gangbiao/cvmfs,ruvolof/cvmfs,trshaffer/cvmfs,MicBrain/cvmfs,ruvolof/cvmfs,Gangbiao/cvmfs,DrDaveD/cvmfs,Gangbiao/cvmfs,reneme/cvmfs,bbockelm/cvmfs,btovar/cvmfs,cvmfs/cvmfs,trshaffer/cvmfs,DrDaveD/cvmfs,Moliholy/cvmfs,alhowaidi/cvmfsNDN,djw8605/cvmfs,MicBrain/cvmfs,cvmfs/cvmfs,btovar/cvmfs,alhowaidi/cvmfsNDN,cvmfs-testing/cvmfs,cvmfs/cvmfs,btovar/cvmfs,MicBrain/cvmfs,Moliholy/cvmfs,cvmfs-testing/cvmfs,Gangbiao/cvmfs