[services] Lib - Tunnelbroker - Use database manager

Summary:
Depends on D3989

Inheriting from DatabaseManagerBase in the tunnelbroker to avoid the boilerplate and reuse common methods.

Test Plan:
You should be able to build tunnelbroker properly

cd services
yarn run-tunnelbroker-service

Reviewers: palys-swm, geekbrother

Reviewed By: palys-swm, geekbrother

Subscribers: ashoat, palys-swm, Adrian, atul, yayabosh

Differential Revision: https://phabricator.ashoat.com/D3990