nut: add linting and fix whitespace and typos

nut: add linting and fix whitespace and typos

shellcheck is a useful linter if a bit pedantic and overzealous so
add overrides to silence false positives

Also, fix issues found by the linting.

* misspelling meant initscript could skip updating configuration in
  certain circumstances
* minor: assignment of the result of execution as the time of creating
  local. This has been separated.

Fix whitespace and comment typos
Fix typo in Config.in option text
* This is cosmetic, but user-facing (for users building via SDK or
  buildroot).

Signed-off-by: Daniel F. Dickinson <redacted>