Add pip and gcovr to slc6_x86_64 docker image
Add pip and gcovr to slc6_x86_64 docker image

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