Unable to mount read only csi volumes

[jhaezebr]

When adding csi volumes to nf-nomad, the chosen access mode is alway 'multi-node-multi-writer'. For read-only shares, this should be 'multi-node-reader-only'. Would it be possible to add a toggle to the specification to allow read-only volumes?

Current volume specification in nf-nomad job

``` "Volumes": { "vol_0": { "Name": "", "Type": "csi", "Source": "nf_scratch_volume", "ReadOnly": false, "AccessMode": "multi-node-multi-writer", "AttachmentMode": "file-system", "MountOptions": null, "PerAlloc": false }, "vol_1": { "Name": "", "Type": "csi", "Source": "nf_reference_volume", "ReadOnly": false, "AccessMode": "multi-node-multi-writer", "AttachmentMode": "file-system", "MountOptions": null, "PerAlloc": false } } ```

Proposed toggle idea in config:

nomad { jobs { volumes = [ { type "csi" name "nf_scratch_volume" path "/scratch" }, { type "csi" name "nf_reference_volume" path "/references" readonly true } ] } }