This fixes a few unrelated issues:
- when ENABLE_MACHINED is false, machinectl is not installed, but _sd_machines
is still used in a few places that want to complete -M and such.
Also, bash completion calls machinectl in various places.
Make missing machinectl mean "no machines" in this case, so
that no error is generated in the callers.
- machinectl list --full would print multiple lines of output per machine,
breaking grep, issue introduced in e2268fa437.
Using --max-addresses=1 would fix the issue, but let's use
--max-addresses=0 because we now can.
- the lists used in various places were slightly different for no good reason.
- don't use a subshell if not necessary.
The code for bash still uses the same combined list of images and running
machines for various commands. The zsh code uses images for start/clone, and
running machines for the rest. Maybe something to fix in the future.
Replaces #25048.
- Don't redefine helpers on every call
- Prefix helper names with main function name
- Adjust some helper names for consistency and convention adherance
Instead of having two different listings of machines, use an autoloaded
function that can be used by other shell completions in the future. It
will also allow editing a single file to change the way machinectl and
systemd-run completion for machines.
