Refactor --debug arg declaration to store const

[shreyb]

jobsub_lite/lib/get_parser.py

Line 215 in e260b99

action=ConvertDebugToVerbose,

We noticed that there is an action here that that converts --debug to --verbose 1. We probably don't need that. Since in the preceding statement, --verbose is established, with a default of 0, we could probably rewrite --debug as a store_const action, with value 1 and dest="verbose".

See https://github.com/fermitools/Ferry-CLI/blob/master/ferry_cli/helpers/auth.py#L183 for an example of how this could be done.

This would allow us to simplify the code and get rid of a custom action.