change from t0temp to unmerged

We only use a single EOS instance for Tier0 and regular production
at CERN now. It's easier if both systems use the same space for
unmerged files, therefor change the Tier0 from t0temp to unmerged.
Merge pull request #4069 from hufnagel/t0temp-unmerged

change from t0temp to unmerged