"lei export-kw" no longer completes for anonymous sources.
More commands use "lei refresh-mail-sync" as a basis for their
completion work, as well.
";AUTH=ANONYMOUS@" is stripped from completions since it was
preventing bash completion from working on AUTH=ANONYMOUS IMAP
URLs. I'm not sure if there's a better way, but all of our code
works fine without specifying AUTH=ANONYMOUS as a command-line
arg.
Finally, we fallback to using more candidates if none can
be found, allowing multiple URLs to be completed.