Fix modules.useradd so that `home` isn't overloaded with multiple meanings
and then allow states.user to support `createhome` as an alternative to
the multiple meanings of `home`.

This also fixes the edge-case that useradd would under specific
circumstances create a home directory called "True".
Merge pull request #5342 from jdelic/feature/fix-useradd-homedirs

Fix useradd handling of home directories