Add bash function that has been deleted from main script

In this repository, we use the backups_role capability to inject a custom script into the main backup script using the variable backups_role_script_prepare_template.

With release 1.2.5, backups_role removed the function title that we use in our custom script. Specifically this commit.

With this MR we add the title function directly to our custom script instead of relying on the main script, which could change and break everything.