tests: boot_sector_test: avoid crashing if status is not available yet

If test case was started in paused mode (-S CLI option) and then
allowed to continue via QMP, boot_sector_test could assert on
transient state with following error:

   assertion failed (qdict_get_try_str(qret, "status") == "running"): (NULL == "running")

Instead of crashing test if 'status' is not available yet, skip check
and repeat iteration again after TEST_DELAY has elapsed.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20230112140312.3096331-14-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

tests/qtest/boot-sector.c

@@ -160,7 +160,9 @@ void boot_sector_test(QTestState *qts)
         qrsp = qtest_qmp(qts, "{ 'execute': 'query-status' }");
         qret = qdict_get_qdict(qrsp, "return");
         g_assert_nonnull(qret);
-        g_assert_cmpstr(qdict_get_try_str(qret, "status"), ==, "running");
+        if (qdict_get_try_str(qret, "status")) {
+            g_assert_cmpstr(qdict_get_try_str(qret, "status"), ==, "running");
+        }
         qobject_unref(qrsp);
 
         g_usleep(TEST_DELAY);