Correct "wait until finished" syntax (e. g. 'wait_for_trigger')

[e-raser]

• For 1) I asked the addon author once again, see Samba Backup: Create and store backups on a Samba share - #364 by e-raser. That extensive exclude_addons list is extremely unhandy and not “that smart”.

• For 2) after triggering the backup I use

wait_for_trigger:
  - platform: state
    entity_id: sensor.samba_backup
    to: IDLE

and send a notification afterwards.