Update to new LCG build and CI
Currently docs and CI assume LCG_102b which is obsolete, should use 104c (but only on cc7 or el9), or 104a_cuda (el8) Also the CI doesn't get the right nodes with cvmfs
Currently docs and CI assume LCG_102b which is obsolete, should use 104c (but only on cc7 or el9), or 104a_cuda (el8) Also the CI doesn't get the right nodes with cvmfs