Update Workflow Manager to use an embedded ActiveMQ broker.

[brosenberg42]

There is not an easy way to added OIDC support to the standalone ActiveMQ management Web UI. Switching to using an embedded ActiveMQ broker enables us to use Hawtio, which has more features than the ActiveMQ Web UI. It also integrates with Spring Security so it can be protected by Workflow Manager's OIDC support. Currently, Workflow Manager is the sender or recipient of all ActiveMQ messages, so embedding ActiveMQ in Workflow Manager prevents a network hop on all messages.