hardcoded ca-volume mountpath /etc/grid-security/certificates makes the reaper to fail deletion in some RSEs

[marcoverl]

the line https://github.com/rucio/helm-charts/blob/master/charts/rucio-daemons/templates/reaper.yaml#L117 erases the existing /etc/grid-security/certificates area when used to mount the ca-bundle.ctr via secret, making the repaer to fail the deletion in some RSEs that probably require the full content of the /etc/grid-security/certificates directory and not simply the CA bundle. It would be better to make it configurable via values.yaml