client: do not wait forever if daemon is not started

client: do not wait forever if daemon is not started

Currently plymouth --wait will wait forever if daemon is not
started. This does not look right - we were asked to wait for
daemon to stop and daemon is obviously stopped. So make it
exit right away in this case.

This avoids timeouts during systemd boot if plymouth happened to be
stopped (or never started) before plymouth-quit-wait had chance to
start.

Signed-off-by: Andrey Borzenkov <arvidjaar@gmail.com>