[FIX] disable OpenMP again for ILPDCWrapper

- it was re-enabled in 0ce469d0ee54f70ee5848639f02537e5451ad44a however
  the underlying issue still does not seem to be solved.
- see also bug #595
Merge pull request #689 from hroest/fix/OpenMP

[FIX] disable OpenMP again for ILPDCWrapper (see also #595)