Jenkins timeout shouldn't rescue Net::HTTP timeout

There is a bug in the current `timeout` functionality in the `Jenkins::Helper::wait_until_ready!` for cases where an `Net::Http` request itself hits a `Net::ReadTimeout < Timeout::Error` or `Net::OpenTimeout < Timeout::Error` (which happens when trying to access Jenkins after a restart on slow machines). The default `read_timeout` on MRI ruby is `60 seconds` so no matter what value you set `node['jenkins']['executor']['timeout']` to, it can never be longer that `60 seconds` when the URL being requested hits a low level `Net` timeout.

This fixes our `Timeout::Error` catching logic to only capture our own defined `JenkinsTimeout` and also within that given timeout block, to allow http requests to `Timeout::Error` without breaking our larger timeout block.