add include guards in catalog_traversal.h
add include guards in catalog_traversal.h

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