When the notifications exchange is created on RabbitMQ by our container
setup script, it receives a Durable: true feature. We mirror this
behavior when we declare the exchange.
This fixes the following issue:
Channel error: (406, "PRECONDITION_FAILED - inequivalent arg 'durable'
for exchange 'notifications' in vhost 'dev': received 'false'
but current is 'true'")