By running ProofBench on the CAF with Jan we have found a couple of issues
due to the fact that we need to use XROOTD also to access (in write) local
files.

make_event_trees.C
   - use TFile::Open to create the files instead of the TFile constructor.

Run_Node_Tests.C
   - use consistently basedir everywhere.


git-svn-id: http://root.cern.ch/svn/root/trunk@15508 27541ba8-7e3a-0410-8455-c3a389f83636