Refactor user provider using more modern shellout syntax

- refactor check_lock to be more ruby-ish locked?
- refactor run_command to use methods from chef/mixin/shell_out

[refs CHEF-4109]
[CHEF-4109] add (un)lock_user|pass to user provider

Deprecates :lock and :unlock actions in favor of the
more precise :lock_user and :lock_pass actions.

On Ubuntu, :lock acts on the user password, whereas on
other platforms it falls back to :lock_user.
whitespace changes and comment removal
[CHEF-4109] Add Illumos user provider