archive: reorganizing the final tarball archive

Adding a top level directory to the tarball archive to avoid
any other element in the tarball root

Change-Id: If14717e8a9bc790e12c84c1fbaa968d786bed96f
Bug-Url: https://bugzilla.redhat.com/1168660
Signed-off-by: Simone Tiraboschi <stirabos@redhat.com>