Fix shellcheck issues in airmon-ng

[Mister-X-]

Description

There are still a few things to fix in airmon-ng, that were reported by shellcheck. They are ignored for the time being so that linting (#2501) won't fail.

This is just to keep track of them so they're not forgotten in the code. There are approximately 20 of them (Search for disable=).

[wileyhy]

One of these was fixed with #2551

[wileyhy]

Here's a current list as of today.

 $ grep -oEe 'disable=(SC)?[0-9]{4}' ./scripts/airmon-ng.linux | sort | uniq -c
      8 disable=2009
      1 disable=2012
      4 disable=2045
      2 disable=2059
      1 disable=2166
      2 disable=2181

[ZeroChaos-]

As noted in the comments, some of those are correct and NOT going to be removed due to compatibility requirements. Just grepping for disable is not providing an accurate list. Off the top of my head all the warnings about ps simply don't apply to us.

[wileyhy]

Okay. ...that's true, some systems still don't have pgrep yet

[ZeroChaos-]

It's mostly that isn't not default and I didn't want to force the install. The warning is right, ps is harder to use, but it does work :-)