systemctl: process all units matched by a glob in the cat verb by default

systemctl: process all units matched by a glob in the cat verb by default

Originally, `systemctl cat` would match only active units, for example:

$ systemctl cat sshd.service

would cat the sshd.service unit file even if the service was inactive.
However:

$ systemctl cat ssh*

would show it only if it was active.

Let's unify the behavior and cat all unit files regardless of a state,
if no state was given explicitly to filter.