Make openrc more robust for grenade scenarios
Make openrc more robust for grenade scenarios

This makes openrc more robust for the grenade scenarios by having a
sane fallback when stackrc is not found.

Change-Id: I297ba519d581d2b6fb4d80d59434acace054bada

group-policy/devstack,nawawi/openstack,richliu/devstack,dtroyer/devstack,richliu/devstack,openstack-dev/devstack,noironetworks/devstack,openstack-dev/devstack,group-policy/devstack,dtroyer/devstack,noironetworks/devstack,nawawi/openstack