Fixed map a path that has been already mapped

| Q               | A
| --------------- | ---
| Bug fix?        | yes
| New feature?    | no
| BC breaks?      | no
| Deprecations?   | no
| Tests pass?     | yes
| Related tickets |
| License         | GNU GPLv3

It appears after `setup` that read the `/etc/setup/setup.rc` file with Windows path for the cache directory ([ref][0]).

[0]: https://ci.appveyor.com/project/alquerci/cyg-apt/build/1.0.190/job/4c85isv4adi9e3kl#L842