Description of problem (please be detailed as possible and provide log
snippets):

With OCS 4.7.2 (https://bugzilla.redhat.com/show_bug.cgi?id=1970583) and OCS 4.8 (https://bugzilla.redhat.com/show_bug.cgi?id=1936858), the kv-v2 secret engine API is now supported for cluster-wide encryption with KMS. In order to successfully deploy a cluster in this case, the VAULT_BACKEND parameter has to be set to v2 in the ocs-kms-connection-details configmap. 

   $ oc get cm ocs-kms-connection-details -o yaml
   apiVersion: v1
   data:
     KMS_PROVIDER: vault
     KMS_SERVICE_NAME: vault
     VAULT_ADDR: https://vault.qe.rh-ocs.com:8200
     VAULT_BACKEND: v2
     VAULT_BACKEND_PATH: test-kv2
     VAULT_CACERT: ocs-kms-ca-secret-znu27r
     VAULT_CLIENT_CERT: ocs-kms-client-cert-7od4d
     VAULT_CLIENT_KEY: ocs-kms-client-key-8obbs
     VAULT_NAMESPACE: ocs
     VAULT_TLS_SERVER_NAME: vault.qe.rh-ocs.com

This is currently done by editing the configmap once it is created during the storagecluster creation. It would be good to have an option in the UI, which will allow the user to set this parameter while configuring the vault details in the storagecluster creation page, instead of having to edit it in the configmap directly.

Version of all relevant components (if applicable):
OCP: 4.8.0-0.nightly-2021-06-19-005119
OCS: ocs-operator.v4.8.0-424.ci

Does this issue impact your ability to continue to work with the product
(please explain in detail what is the user impact)?
Yes, without the UI option available, the deployment would not succeed in such a case unless the configmap is not edited manually.

Is there any workaround available to the best of your knowledge?
Yes, edit the ocs-kms-connection-details configmap to add the parameter

Rate from 1 - 5 the complexity of the scenario you performed that caused this
bug (1 - very simple, 5 - very complex)?
3

Can this issue reproducible?
Yes

Can this issue reproduce from the UI?
Yes

If this is a regression, please provide more details to justify this:
No

Steps to Reproduce:
Steps to Reproduce:
1. Create a backend path in Vault with kv-v2
   $ vault secrets enable -path=test-kv2 kv-v2
   Success! Enabled the kv-v2 secrets engine at: test-kv2/

2. Enter the path created above when deploying OCS with cluster wide encryption using KMS enabled in UI

3. Check the status of the OSD pods

Actual results:
The OSD pods don't come up and fail with the following error, since the VAULT_BACKEND parameter is not set to v2:

$ oc logs  rook-ceph-osd-0-54f9f6c6c-hrnw2 -c encryption-kms-get-kek
["Invalid path for a versioned K/V secrets engine. See the API docs for the appropriate API endpoints to use. If using the Vault CLI, use 'vault kv get' for this operation."] 

Expected results:
The UI should have an option to set VAULT_BACKEND value, to avoid deployment failure