action: Simplify the code

action: Simplify the code

Replace action_str_from_arg() and action_get_first_arg() with
action_get_str().

Two reasons:

- This optimization reduces neither LOC nor amount of work done during
  the arguments processing, but requires two additional functions.

- Logging only the first argument of an action creates an illusion that
  only one argument was given. Instead of confusing the user just log
  the fact that the action is being handled.