Revert "Re-enable xrootd 4.0.2."
Merge pull request #940 from cms-sw/revert-922-re-enable_xrootd402_72X

Revert "Re-enable xrootd 4.0.2."
Merge remote branch 'origin/IB/CMSSW_7_2_X/stable' into IB/CMSSW_7_0_X/stable