iotests: fix race in 030

the stop_test case tests that we can resume a block-stream
command after it has stopped/paused due to error. We cannot
always reliably query it before it finishes after resume, though,
so make this a conditional.

The important thing is that we are still testing that it has stopped,
and that it finishes successfully after we send a resume command.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/030

@@ -245,6 +245,7 @@ class TestEIO(TestErrors):
         while not completed:
             for event in self.vm.get_qmp_events(wait=True):
                 if event['event'] == 'BLOCK_JOB_ERROR':
+                    error = True
                     self.assert_qmp(event, 'data/device', 'drive0')
                     self.assert_qmp(event, 'data/operation', 'read')
 
@@ -257,9 +258,11 @@ class TestEIO(TestErrors):
                     self.assert_qmp(result, 'return', {})
 
                     result = self.vm.qmp('query-block-jobs')
+                    if result == {'return': []}:
+                        # Race; likely already finished. Check.
+                        continue
                     self.assert_qmp(result, 'return[0]/paused', False)
                     self.assert_qmp(result, 'return[0]/io-status', 'ok')
-                    error = True
                 elif event['event'] == 'BLOCK_JOB_COMPLETED':
                     self.assertTrue(error, 'job completed unexpectedly')
                     self.assert_qmp(event, 'data/type', 'stream')