Unable to install Keybase rpm via rpm-ostree on Fedora Atomic (Workstation) due to /opt path

See https://github.com/projectatomic/rpm-ostree/issues/233 for more context.

System is Fedora Atomic Workstation release 27 fully upgraded to current with `sudo atomic host upgrade`.

Steps taken:

```
cd Downloads
curl -O https://prerelease.keybase.io/keybase_amd64.rpm
sudo rpm-ostree install keybase_amd64.rpm
[sudo] password for user:
error: Unsupported path: /opt/keybase/Keybase; See https://github.com/projectatomic/rpm-ostree/issues/233
```

Start with the reported rpm-ostree issue 233 and reproduce the `rpm-ostree install keybase_amd64.rpm` command on Fedora Atomic Workstation. Compare the package's `/opt/keybase/Keybase` path with rpm-ostree's supported paths; done means the Keybase RPM installs successfully without the unsupported-path error.

Written by the indexing model from the issue text.