When mixing Imperative bindings for blob and Declarative bindings for Queue messages, queue messages are written first even when Blob messages are explicitly flushed

I am using a binder to construct the blob name at runtime in my Azure Function. Additionally, I have a queue binding that is declarative. I write to the blob and then flush and close the text writer. Then I add the queue message to the collection. However, the queue message is written before the blob, resulting in the next function in the chain seeing an error.

#### Investigative information

- Timestamp: 2017-09-30T00:21:00Z
- Invocation ID:
bc72ea3d-0170-4e30-9a4e-6c78504b8498 (parent job, which publishes blob & queue).
4b77107d-4a80-433a-8bf4-d50c2788b84f (sample queue message job)
- Region: NCUS

#### Repro steps

1. Create an Azure Function
2. Set an Azure Queue as the output.
3. Have the function output a blob using a binder.
4. Write to the blob, and then the queue. Example:

` using (var writer = await binder.BindAsync(attributes))
{
writer.Write(output);
writer.Flush();
writer.Close();
}

await outputQueueItem.AddAsync(new SomePoco {Name = blobName});
`
5. Create an Azure Function which takes a QueueMessage with SomePoco as a trigger, and takes a blob with the Name of SomePoco as input.

#### Expected behavior

I expect the write to the blob to be blocking, and for the queue message to be written after the blob has been written.

#### Actual behavior

The blob messages are not written until the parent function completely finishes execution. While the queue messages are written while the parent function is still running.

#### Known workarounds

Have a copy of the function which processes the SomePoco queue messages, except it accepts input from the poison queue message stream. Then use this to manually clear out poison queue messages.

#### Related information

Provide any related information

* Programming language used: C#

Start by running the five-step reproduction with an Azure Function using a binder for the blob and a declarative queue output. Trace when each output is persisted relative to function completion; done means the blob is written before the queued message is published, so the downstream function can read it successfully.

Written by the indexing model from the issue text.