journalctl: allow globbing in --unit and --user-unit

journalctl: allow globbing in --unit and --user-unit

This is a continuation of e3e0314b systemctl: allow globbing in commands
which take multiple unit names.

Multiple patterns can be specified, as separate arguments, or as one argument
with patterns seperated by commas.

If patterns are given, at least one unit must be matched (by any of the patterns).
This is different behaviour than systemctl, but here it is necessary because
otherwise anything would be matched, which is unlikely to be the intended
behaviour.

https://bugs.freedesktop.org/show_bug.cgi?id=59336