route-manager/test: fix usage of g_assert_expect_message()

Tests that use g_assert_expect_message() must initialize with
nmtst_init_assert_logging().

Otherwise, the caller can change the logging level via
  NMTST_DEBUG=log-level=DEBUG,log-domains=DEFAULT
which breaks the assertions.

nmtst_init_assert_logging() allows the caller to turn of
checking of assertions via
  NMTST_DEBUG=log-level=DEBUG,log-domains=DEFAULT,no-expect-message

Also, don't use g_message() in platform tests otherwise the test fail
because nmtst now sets g_log_set_always_fatal().

src/platform/tests/test-common.c

@@ -263,10 +263,10 @@ main (int argc, char **argv)
 		nmtst_reexec_sudo ();
 
 #ifdef REQUIRE_ROOT_TESTS
-		g_message ("Fail test: requires root privileges (%s)", program);
+		g_print ("Fail test: requires root privileges (%s)\n", program);
 		return EXIT_FAILURE;
 #else
-		g_message ("Skipping test: requires root privileges (%s)", program);
+		g_print ("Skipping test: requires root privileges (%s)\n", program);
 		return 77;
 #endif
 	}

src/tests/test-route-manager.c

@@ -676,7 +676,7 @@ fixture_teardown (test_fixture *fixture, gconstpointer user_data)
 void
 init_tests (int *argc, char ***argv)
 {
-	nmtst_init_with_logging (argc, argv, NULL, "ALL");
+	nmtst_init_assert_logging (argc, argv, "WARN", "ALL");
 }
 
 void