Revert "tests: add qmp/qom-set-without-value test"

Markus spotted some issues with this new test case which
unfortunately I didn't notice had been flagged until after
I'd applied the pull request. Revert the relevant commit.

This reverts commit 2b70ea92766f5a1a735a44e28c92cdfba3c4054f.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/tests/qmp-test.c b/tests/qmp-test.c
index 2b923f0..b347228 100644
--- a/tests/qmp-test.c
+++ b/tests/qmp-test.c
@@ -321,19 +321,6 @@
     qtest_quit(qs);
 }
 
-static void test_qom_set_without_value(void)
-{
-    QTestState *qts;
-    QDict *resp;
-
-    qts = qtest_init(common_args);
-    resp = qtest_qmp(qts, "{'execute': 'qom-set', 'arguments':"
-                     " { 'path': '/machine', 'property': 'rtc-time' } }");
-    g_assert_nonnull(resp);
-    qmp_assert_error_class(resp, "GenericError");
-    qtest_quit(qts);
-}
-
 int main(int argc, char *argv[])
 {
     g_test_init(&argc, &argv, NULL);
@@ -341,7 +328,6 @@
     qtest_add_func("qmp/protocol", test_qmp_protocol);
     qtest_add_func("qmp/oob", test_qmp_oob);
     qtest_add_func("qmp/preconfig", test_qmp_preconfig);
-    qtest_add_func("qmp/qom-set-without-value", test_qom_set_without_value);
 
     return g_test_run();
 }