installer: Fix installed and media version

Previously the installed version and the version of the media were mixed
up in the wording of the installer.
Now the versions are used correctly.

rhbz#967390

Change-Id: I4a414b93e88da60d8aaadd62e5a32d222334c532
Signed-off-by: Fabian Deutsch <fabiand@fedoraproject.org>