Fix jetty redeploy with custom jetty-env.xml

[aindlq]

Redeploy would fail because runner classloader is separate from the servlet container classloader. So runner was not able to create new WebAppContext.

[f4lco]

Thank you. I'll need some more time - let me get back to you next week!

[boris-petrov]

That makes sense to me. It's similar to 0126e07. Perhaps the:

ClassLoader oldClassLoader = Thread.currentThread().getContextClassLoader()
Thread.currentThread().setContextClassLoader(cl)
try {
  ...
}
finally {
  Thread.currentThread().setContextClassLoader(oldClassLoader)
}

Logic can be extracted in a method - I see it's already used in 3 other places.

[f4lco]

Thank you for your contribution!