Mount cloudsql volume instead of all volumes

[sl0wik]

Using --volumes-from overwrite image workspace with empty workspace. This change mounting only /cloudsql.

[moliver-hemasystems]

Is there a particular volume that should be excluded to prevent replacing the image's pre-existing workspace? This is impacting our ability to run serverless exec to run rake commands on our rails app images which are using a custom entrypoint. Because the workspace is being replaced, not only can our entrypoint not be found, but I suspect it wouldn't find our rake tasks either.