This script behaves the same way as our custom standby script, with a few
modifications, for example:
* instead of using initscripts to stop/start daemons, it uses systemctl calls
* save variables that are needed when resuming in /tmp, because the script is
executed twice instead of once (when suspending and when resuming)
* remove the locking/unlocking of the critical section and the actual state
change, since that is handled by systemd-suspend now
Also, add a different standby script for when systemd is enabled. Said script
acts as a wrapper for systemd's suspend mechanism.
https://jira.digi.com/browse/DEL-6415
Signed-off-by: Gabriel Valcazar <gabriel.valcazar@digi.com>