Fix multiple MPI ranks per node with OpenCL

Fix multiple MPI ranks per node with OpenCL

Similarly to the thread-MPI case, the source of the issue was
the hardware detection broadcasting the outcome of GPU detection
within a node. The MPI platform and device IDs, OpenCL internal
entities, differ across processes even if both platform and device(s)
are shared. This caused corruption at context creation on all ranks
other than the first rank in the node (which did the detection).

This change disables the GPU data broadcasting for OpenCL with MPI.

Fixes #1804

Change-Id: I90defdcb3515796c46ba89efb0ed1e3c8b1b35f9