add CVMFS_FALLBACK_PROXY to parameters displayed by 'cvmfs_config showconfig'
add CVMFS_FALLBACK_PROXY to parameters displayed by 'cvmfs_config showconfig'

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