tests: fix check-qobject leak

/public/qobject_is_equal_conversion: OK

=================================================================
==14396==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 56 byte(s) in 1 object(s) allocated from:
    #0 0x7f07682c5850 in malloc (/lib64/libasan.so.4+0xde850)
    #1 0x7f0767d12f0c in g_malloc ../glib/gmem.c:94
    #2 0x7f0767d131cf in g_malloc_n ../glib/gmem.c:331
    #3 0x562bd767371f in do_test_equality /home/elmarco/src/qq/tests/check-qobject.c:49
    #4 0x562bd7674a35 in qobject_is_equal_dict_test /home/elmarco/src/qq/tests/check-qobject.c:267
    #5 0x7f0767d37b04 in test_case_run ../glib/gtestutils.c:2237
    #6 0x7f0767d37ec4 in g_test_run_suite_internal ../glib/gtestutils.c:2321
    #7 0x7f0767d37f6d in g_test_run_suite_internal ../glib/gtestutils.c:2333
    #8 0x7f0767d38184 in g_test_run_suite ../glib/gtestutils.c:2408
    #9 0x7f0767d36e0d in g_test_run ../glib/gtestutils.c:1674
    #10 0x562bd7674e75 in main /home/elmarco/src/qq/tests/check-qobject.c:327
    #11 0x7f0766009039 in __libc_start_main (/lib64/libc.so.6+0x21039)

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20180104160523.22995-9-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
