utest_gpu: make utest MPI-aware

This is not needed for now, but it would be the first stumbling block
when writing an MPI-aware GPU unit test.

utests/utest_gpu.c

@@ -15,6 +15,8 @@
 
 #include "num/init.h"
 
+#include "num/mpi_ops.h"
+
 #include "utest.h"
 
 
@@ -42,8 +44,14 @@ UTESTS_GPU
 #endif
 
 
-int main(int /*argc*/, char* argv[])
+int main(int argc, char* argv[])
 {
+#ifdef USE_MPI
+	init_mpi(&argc, &argv);
+#else
+	(void)argc;
+#endif
+
 	int num_tests_run = 0;
 	int num_tests_pass = 0;
 
@@ -57,6 +65,8 @@ int main(int /*argc*/, char* argv[])
 
 	debug_printf(good ? DP_INFO : DP_ERROR, "%20s: %2d/%2d passed.\n", argv[0], num_tests_pass, num_tests_run);
 
+	deinit_mpi();
+
 	exit(good ? 0 : 1);
 }