- Timestamps are milliseconds in AMQP 1.0, but in AMQP 0.9.1 it is seconds.
  Fixed by multiplying the timestamp by 1 000.
- Shovel crashed if user_id was set in the message because the encoding
  was as utf8 while it should be a byte array.
- Negative integers were encoded as integers - therefore leading to
  incorrect positive values.
- Float values were not supported by the client.
- Fixed priority header encoding in AMQP 1.0. It was set as uint but it
  should be ubyte.
- Priority of the message is now in the Headers instead of Application
  Properties. This is potentially a breaking change.

Fixes: #7508
(cherry picked from commit 8e954ff)

In line with internal RabbitMQ behaviour AMQP defaults to durable
messages.