adjust test case to less stringent checking of writability of the cache directory
adjust test case to less stringent checking of writability of the cache directory

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