Fix release permissions on oslo library projects

Give oslo-core permission to tag releases for
oslo.config and oslo.sphinx.

Change-Id: I4a5edb6c9a54ceda9b08c2707e1fe8da02caa85e
Signed-off-by: Doug Hellmann <doug.hellmann@dreamhost.com>
Reviewed-on: https://review.openstack.org/35538
Reviewed-by: Mark McLoughlin <markmc@redhat.com>
Reviewed-by: Khai Do <zaro0508@gmail.com>
Approved: Monty Taylor <mordred@inaugust.com>
Reviewed-by: Monty Taylor <mordred@inaugust.com>
Tested-by: Jenkins