ARTEMIS-5799 Add broker lifecycle events to ActiveMQServerBasePlugin

[AntonRoskvist]

Added afterStart and beforeStopped methods to ServerBasePlugin. This adds a convenient way of tying plugin lifecycle to the brokers and simplify clean start and stop of whatever the plugin does.

[jbertram]

I think you can do essentially the same thing already using an implementation of org.apache.activemq.artemis.core.server.ActivateCallback. You can see in the code that the callback is invoked right around the same time your new methods are.

To be clear, o.a.a.a.c.s.ActivateCallback#preDeActivate is equivalent to o.a.a.a.c.s.plugin.ActiveMQServerBasePlugin#beforeStopped and o.a.a.a.c.s.ActivateCallback#activationComplete is equivalent to o.a.a.a.c.s.plugin.ActiveMQServerBasePlugin#afterStarted.

[AntonRoskvist]

@jbertram Wow, don't know how I missed that. The ActivateCallback works perfectly. Thanks!

I'll go ahead and close this.

[AntonRoskvist]

Not needed, ActivateCallback already does this.