When a module uses the HttpClient mixin but registers the USERNAME
and PASSWORD datastore options in order to perform a form auth,
it ruins the ability to also perform a basic auth (sometimes it's
possible to see both). To avoid option naming conflicts, basic auth
options are now HTTPUSERNAME and HTTPPASSWORD.
Fix#4885
def peer is a method that gets repeated a lot in modules, so we
should have it in the tcp mixin. This commit also clears a few
modules that use the HttpClient mixin with def peer.
See the complaint on #4039. This doesn't fix that particular
issue (it's somewhat unrelated), but does solve around
a file parsing problem reported by @void-in