Change "--really-do-this" for "--write" for drive and sync tools

The --really-do-this doesn't always make sense for some of the operations. Also, docopt will allow --r as a shortcut which could be misinterpreted as --read-only.

Change the command-line arg to --write. Also, change use of var read_only to write_mode to avoid unnecessary negation between option and python variable.

This should be done to both drive tool and sync tool for consistency.

This will also require changes to schedule CI and CI var naming - coordinated with version changes of tools.