Stupid formalism
Fix XROOTStorage: putFile puts files in wrong place on EOS

In some cases the Path checked here already starts with //, so this check would
fail and the rootdir would be prepended again.  This results in files ending up
in the wrong place.
Merge pull request #2204 from andresailer/XRootFix

[v6r11] XRootStorage: putFile would place file in the wrong location on eos