Provide password capacity parameter to set password command

[nathanlcarlson]

Password capacity parameter defaults to 16 if not provided and will result in truncated passwords.

[jhoblitt]

If this conditional is evaluated first, the value of $real_password.length would always be <= 20. That would allow one of the conditional statements to be removed. E.g.

  if $real_password.length > 20 {
    fail('ipmi v2 restricts passwords to 20 or fewer characters')
  }
  if $real_password.length <= 16 {
    $password_capacity = '16'
  } else {
    $password_capacity = '20'
  }

[nathanlcarlson]

Good call. I also re-ordered such that the unless_command is right next to the place it is used. I've squashed these commits together to tidy this up.