[jmxfetch] `run()` will be non-static for App

[truthbk]

This is a very small PR to address a small change we expect to implement in the JMXFetch lib, by which the App.run() method will no longer be static. It is currently a nasty piece of code we have in JMXFetch we would like to get rid of. It should be of minor impact as it still seems very self contained within the tracer use of the lib.

[truthbk]

note: I can see the tests failing until we actually release the new JMXFetch version.

[truthbk]

This is the PR on the jmxfetch side: https://github.com/DataDog/jmxfetch/pull/376

[mcculls]

Closing as stale, this change was applied in #3236