Trunk fails

[Bokor Andras]

Hi all, Trunk currently fails without -DskipShade.To see the full error message 
check one of the pre-commit buils, 
eg:https://builds.apache.org/job/PreCommit-HADOOP-Build/12839/artifact/patchprocess/branch-mvninstall-root.txtand
 look for "Duplicate classes found" string.It's related to shading. I do 
not know too much about shading so I need some help to invesitage this. 
Thanks,Andras