The edpm-ansible code that generates nova-compute's config.json (the kolla thing) doesn't provide a mechanism for adding additional volume mounts, and this is a regression from RHOSP's tripleo deployments.

Background:

Tripleo provides the ability to add volume mounts to the nova_compute service, and that feature is used by some cinder backends. Specifically, Dell EMC's PowerFlex backend requires os-brick have access a credentials file at a fixed location on the host. The Dell team has been able to get the credentials file installed on an EDPM compute node, but the nova_compute container is unable to access the file.

The suggested fix is to support a new "edpm_nova_compute_extra_volumes" ansible variable that a cloud admin can use to add additional volume mounts to nova_compute.