Extract option parser initialization
Extract option parser initialization

The `parse_arguments` method of the `CLI` class was rather long due to
the inline initialization of the `OptionParser`.

Extracting this initialization into a separate method makes it clearer
that the purpose of the `parse_arguments` method is to simply parse
arguments and handle invalid arguments if they are provided.

Change-Id: Icf095dc76226987c01fc7011e99db88c723eda12
Reviewed-on: https://gerrit.causes.com/31534
Tested-by: jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@causes.com>
Reviewed-by: Shane da Silva <6f6e68d1df92f30cb4b3ce35260ddf94a402f33d@causes.com>

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