[services][refactoring] Tunnelbroker - AMQP Manager refactoring into a class.

Summary:
Refactoring AMQP Manager global functions into a class.

Linear task: ENG-589

Depends on D3124

Test Plan: Successfully built the service and run it with a successful connection to the AMQP server.

Reviewers: karol-bisztyga, palys-swm, ashoat

Reviewed By: palys-swm, ashoat

Subscribers: benschac, ashoat, palys-swm, Adrian, atul, karol-bisztyga

Differential Revision: https://phabricator.ashoat.com/D3157