cleanup: use index instead of value while iterating
cleanup: use index instead of value while iterating

This commit cleans up for loop to use index to access
value instead of copying value into a new variable
while iterating.
```
internal/util/csiconfig.go:103:2: rangeValCopy: each \
iteration copies 136 bytes (consider pointers or indexing) \
(gocritic)
        for _, cluster := range config {
```

Signed-off-by: Rakshith R <2c7b05ed1488c7110901626c2c56645675e22767@redhat.com>

ceph/ceph-csi,ceph/ceph-csi,ceph/ceph-csi,ceph/ceph-csi