Revert "Revert "adding an MPI init test in case of that MPI was initialized repeatedly""

This reverts commit 23ebe452a5.

Source/Common/Include/MPIWrapper.h

@@ -112,7 +112,12 @@ namespace Microsoft { namespace MSR { namespace CNTK {
             fprintf(stderr, "MPIWrapper: initializing MPI\n"); 
             fflush(stderr);
 
-            MPI_Init_DL() || MpiFail("mpiaggregator: MPI_Init");
+			int flag = 0;
+			MPI_Initialized(&flag);
+			if (!flag)
+			{
+				MPI_Init_DL() || MpiFail("mpiaggregator: MPI_Init");
+			}
             MPI_Comm_rank(MPI_COMM_WORLD, &m_myRank);
             MPI_Comm_size(MPI_COMM_WORLD, &m_numMPINodes);
             m_numNodesInUse = m_numMPINodes;