Add autosave config option

[botastic]

ironicbadger#14

Allows Ansible to add the autosave configuration option to /etc/snapraid.conf.

For context, this option autosaves the state when scrubbing and syncing once it's processed the amount of GB specified. This is particularly useful when doing long syncs protecting against sudden crashes, power loss, etc: https://www.snapraid.it/manual#7.10

Currently, the feature is off by default as marked by snapraid_autosave.enabled.