help text for juju list-users needs improving

[Peter Matulis]

e.g.:

Usage: juju list-users [options]

Summary:
Lists Juju users allowed to connect to a controller.

Options:

--all (= false)
    Include disabled users
-c, --controller (= "")
    Controller to operate in
--exact-time (= false)
    Use full timestamp for connection times
--format (= tabular)
    Specify output format (json|tabular|yaml)
-o, --output (= "")
    Specify output file

Details:
By default, the tabular format is used.

Examples:

    juju list-users

See also: add-user
          register
          show-user
          disable-user
          enable-user

[Reed O'Brien (reedobrien)]

PR: https://github.com/juju/juju/pull/5077
RB: http://reviews.vapour.ws/r/4520/

[Cheryl Jennings (cherylj)]

PR: https://github.com/juju/juju/pull/5140