Fixes 500 Error on overlapping columns during join

When joining datasets which have overlapping columns, bamboo raises a 500 error.
This fixes it but it seems *way* too permissive (catches all `Exception`) so please take this more as a bug report than a patch.

Unfortunately, the root exception is not specific and resides in pandas:
```
  File "/Volumes/data/src/envs/bamboo/lib/python2.7/site-packages/pandas/core/internals.py", line 1197, in _maybe_rename_join
    raise Exception('columns overlap: %s' % to_rename)
Exception: columns overlap: Index([_submission_time, _uuid, meta_instanceid], dtype=object)
```