test_qom_set_without_value() is about a bug in infrastructure used by
the QMP core, fixed in commit c4897802.  We covered the bug in
infrastructure unit tests (commit bce3035a).  I wrote that test
earlier, to cover QMP level as well, the test could go into qmp-test.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>