Cobra adds the commands 'help', '__complete' and '__completeNoDesc'
inside rootCmd.Execute(), however, when kubectl decides if it should
lookup plugins, rootCmd.Execute() had not been called yet. Therefore,
the call to cmd.Find(cmdPathPieces) done by kubectl does not find the
commands added by Cobra. To fix this we must check for them explicitly.
Signed-off-by: Marc Khouzam <marc.khouzam@montreal.ca>
Kubernetes-commit: e703b3d25377e763b117805b3d88fe7236f3ff76