Doc: Update storwize cinder driver configuration
Adding new configuration parameter 'storwize_svc_retain_aux_volume'
to storwize cinder driver configuration guide which is an optional
paramter to retain auxiliary volume in a mirror relationship on delete
of the primary volume or moving the primary volume to non-mirror
- (List) Comma separated list of storage system storage pools for volumes.
* - ``storwize_svc_mirror_pool`` = ``None``
- (String) Specifies the name of the pool in which mirrored copy is stored. Example: "pool2"
+ * - ``storwize_svc_retain_aux_volume`` = ``False``
+ - (Boolean) This defines an optional parameter to retain auxiliary volume in a mirror relationship on the delete of primary volume or moving to non-mirror.
* - ``storwize_peer_pool`` = ``None``
- (String) Specifies the name of the peer pool for hyperswap volume, the peer pool must exist on the other site.
* - ``storwize_preferred_host_site`` = ``{}``
