(#18285) Disable JMX network connector

We were previously exposing JMX information over the network, to no real
end. Nobody was using that feature, and in fact the feature causes
issues on Ubuntu where remote RMI listener threads bind to all
interfaces by default.

We already expose JMX information via REST, and if people want to get at
more detailed stuff they can always use JConsole or the like.

As a bonus, this should result in a few less active threads and a little
less memory used.

Signed-off-by: Deepak Giridharagopal <deepak@puppetlabs.com>