[MERGE] Fix bug #367726 by reverting some default user handling introduced while fixing bug #256612

[Vincent Ladeuil]

>>>>> "robert" == Robert Collins <robert.collins at canonical.com> writes:

    robert> bb:approve

Thanks.

    robert> This may need further work, but I'd like use to be
    robert> careful to avoid providing explicit usernames to
    robert> services where we have no good reason to do so -
    robert> services that are external to bzr can always look it
    robert> up themselves (as ssh does).

I agree with the feeling, using getpass.getuser() has always
seemed strange to my eyes, but I was preserving backward
compatibility here.

I should note though, that if the need is to provide a default
user name for intra-nets (which seems to be the most obvious
addressed case here), authentication.conf may be the way to go.

All that is missing is a way to reference getuser.getpass() from
authentication.conf, but if the goal is to provide a user name we
may as well let the users specify it directly or delegated to any
credential store (authentication.conf is not meant to be shared
between users, by design).

        Vincent