nova.conf: fix incorrect neutron credentials.
nova.conf: fix incorrect neutron credentials.

Nova should use Neutron credentials to interact with Neutron.

Backport: liberty
Closes-Bug: #1512070
Change-Id: I78ec4c032d457b519ccfed9cab190afd65027048

coolsvap/kolla,negronjl/kolla,mrangana/kolla,mandre/kolla,coolsvap/kolla,mandre/kolla,nihilifer/kolla,stackforge/kolla,toby82/kolla,negronjl/kolla,GalenMa/kolla,toby82/kolla,rahulunair/kolla,tonyli71/kolla,toby82/kolla,limamauricio/mykolla,dardelean/kolla-ansible,dardelean/kolla-ansible,intel-onp/kolla,GalenMa/kolla,mrangana/kolla,nihilifer/kolla,tonyli71/kolla,limamauricio/mykolla,stackforge/kolla,openstack/kolla,negronjl/kolla,coolsvap/kolla,openstack/kolla,limamauricio/mykolla,intel-onp/kolla,dardelean/kolla-ansible,stackforge/kolla,mandre/kolla,rahulunair/kolla