ManagementContext should support sslContext injection

If an user wants to use SSL with JMX, the only option today is to configure via the command line (`-Dcom.sun.management.jmxremote.port=xxxx -Dcom.sun.management.jmxremote.ssl=true`).

This configuration doesn't use the `sslContext` meaning that the user might have to duplicate the SSL configuration two times:
- the `sslContext` in `activemq.xml` that can be used in `transportConnector`
- the same configuration via the command line (`com.sun.management.jmxremote*`)

It would be great to be able to inject the `sslContext` in the `` to use an unique configuration.

Something like:

```

```