Just reword some output

swiftmpiproxies.c

@@ -355,7 +355,7 @@ int main(int argc, char *argv[]) {
         /* This call will succeed, if the receive buffer has not been
          * updated. */
         if (datacheck_test(myrank, pcells_size[pid], pcells_in[pid])) {
-          message("Received data is not modified");
+          message("Received data buffer has not been modified");
           fflush(stdout);
           error("Failed");
         } else {