When an agent's launchd.agents.<name>.domain is changed from gui to
user (or the agent is newly installed on a headless macOS system
where the gui/<UID> domain never existed), bootoutAgent attempts to
unload the agent from the old domain first. On such systems, this
fails with: Boot-out failed: 125: Domain does not support specified
action.
The bootoutAgent function only treated "No such process" as a
non-fatal condition (return 2). This change adds the domain-not-exist
error to the same handling path: the agent wasn't running in a domain
that doesn't exist, so we can safely skip the boot-out and proceed
with bootstrap into the new domain.
79e6082586