Enforce the use of `__virtualname__` for modules which rename themselves.
Clarify where the deprecation warning is coming from.
`salt.modules.localemod` is now using `__virtualname__`
`salt.modules.groupadd` is now using `__virtualname__`
`salt.modules.parted` is now using `__virtualname__`
`salt.modules.linux_sysctl` is now using `__virtualname__`
`salt.modules.linux_acl` is now using `__virtualname__`
`salt.modules.saltcloudmod` is now using `__virtualname__`
`salt.modules.apt` is now using `__virtualname__`
`salt.modules.sysmod` is now using `__virtualname__`
`salt.modules.upstart` is now using `__virtualname__`
`salt.modules.useradd` is now using `__virtualname__`
`salt.modules.dpkg` is now using `__virtualname__`
`salt.modules.virtualenv_mod` is now using `__virtualname__`
`salt.modules.cmdmod` is now using `__virtualname__`
`salt.modules.djangomod` is now using `__virtualname__`
`salt.returners.syslog_return` is now using `__virtualname__`
`salt.returners.couchdb_return` is now using `__virtualname__`
`salt.returners.carbon_return` is now using `__virtualname__`
`salt.returners.sqlite3_return` is now using `__virtualname__`