hide default password that's stored in plaintext in this repository

[skyfaller]

linode_create.yml currently has a default user password visible in plaintext in this repository. There are two barriers preventing a bad actor from exploiting this:

• The villain would need a user's private ssh key, since we've disabled password-based login.
• We require users to change their passwords the first time they log in, so the default password should only work on a user account that has never logged in.

That said, this is terrible practice, and we should:

• encrypt the password in a vault
• consider storing the password in the ansible hosts directory, rather than in our repository