Refactor ngrok_running? to re-use ngrok_process_status_lines instead of a shell process

[texpert]

raise_if_similar_ngroks changed to work with nil pid for checking only for Ngrok process with the similar port.

spawn_new_ngrok when running with persistence will fetch the process line matching the specified Ngrok port, thus not taking into account other Ngrok processes, tunnelling on other ports.

[codeclimate]

Code Climate has analyzed commit 02c4233 and detected 1 issue on this pull request.

Here's the issue category breakdown:

Category	Count
Complexity	1

The test coverage on the diff in this pull request is 100.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 92.5% (8.5% change).

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