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.
4e9183059a