Update net/rabbitmq to 3.7.2.

3.7.2
- Bug fix in the HTTP auth backend

3.7.1
- Bug fixes

3.7.0
- Minimum required Erlang version is now 19.3
- Automation-friendly cluster formation
- Distributed management plugin, including minor breaking HTTP API changes.
- Simpler, ini-style configuration format
- Per-vhost limits
- Operator policies
- Topic-based authorisation
- Cross-protocol Shovel (currently supports AMQP 0.9.1 and AMQP 1.0)
- Command-line tools are extensible via plugins
- Message store multi-tenancy
- Proxy protocol support
- Web STOMP no longer supports WebSocket emulation
- Java and .NET client releases no longer track RabbitMQ server releases
- .NET client now supports .NET Core.
- Management plugin extensions now must target Cowboy 2.0
- Java client for RabbitMQ HTTP API

(fhajny)