add repo root detector to common.sh
add repo root detector to common.sh

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