tests: fix migration-test leak

Direct leak of 12 byte(s) in 2 object(s) allocated from:
    #0 0x7f50d403c850 in malloc (/lib64/libasan.so.4+0xde850)
    #1 0x7f50d1ddf98f in vasprintf (/lib64/libc.so.6+0x8098f)
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20180104160523.22995-12-marcandre.lureau@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

tests/migration-test.c

@@ -358,13 +358,14 @@ static void migrate_check_parameter(QTestState *who, const char *parameter,
                                     const char *value)
 {
     QDict *rsp, *rsp_return;
-    const char *result;
+    char *result;
 
     rsp = wait_command(who, "{ 'execute': 'query-migrate-parameters' }");
     rsp_return = qdict_get_qdict(rsp, "return");
     result = g_strdup_printf("%" PRId64,
                              qdict_get_try_int(rsp_return,  parameter, -1));
     g_assert_cmpstr(result, ==, value);
+    g_free(result);
     QDECREF(rsp);
 }