Fix Message Producer

[amannocci]

Motivation:
We forget to add credit header in MessageProducer when we set it with deliveryOptions.
As a result the drain handler will never be call.

Modification:
Add credit header when we set delivery options.

Result:
The drain handler will be call in every situation.

[vietj]

Hi, can you contribute a test + implementation ?

[amannocci]

Tell me what you think about this little fix

[vietj]

looks good to me, however we should make a copy of the options because the same options may be used in two producers leading to problems.

can you add this ? then it will be good for a PR.

[amannocci]

Fixed #1513