use default X509_CERT_DIR also if it is empty string
use default X509_CERT_DIR also if it is empty string

djw8605/cvmfs,cvmfs/cvmfs,Gangbiao/cvmfs,trshaffer/cvmfs,cvmfs/cvmfs,cvmfs/cvmfs,DrDaveD/cvmfs,djw8605/cvmfs,DrDaveD/cvmfs,trshaffer/cvmfs,cvmfs/cvmfs,trshaffer/cvmfs,Gangbiao/cvmfs,DrDaveD/cvmfs,cvmfs/cvmfs,Gangbiao/cvmfs,djw8605/cvmfs,DrDaveD/cvmfs,DrDaveD/cvmfs,trshaffer/cvmfs,trshaffer/cvmfs,DrDaveD/cvmfs,djw8605/cvmfs,cvmfs/cvmfs,DrDaveD/cvmfs,cvmfs/cvmfs,Gangbiao/cvmfs,djw8605/cvmfs,Gangbiao/cvmfs