Fix seting of parallel_run_ member.

We are having a parallel only if there are more than one processes,
and not already with only one.

Kudos to @atgeirr for finding this in the review.

opm/autodiff/SimulatorFullyImplicitBlackoil_impl.hpp

@@ -207,7 +207,7 @@ namespace Opm
                     boost::any_cast<const ParallelISTLInformation&>(solver_.parallelInformation());
                 // Only rank 0 does print to std::cout
                 terminal_output_= (info.communicator().rank()==0);
-                is_parallel_run_ = info.communicator().size();
+                is_parallel_run_ = ( info.communicator().size() > 1 );
             }
         }
 #endif