Describe the bug
DR volume even after activation remains in standby mode if there are one or more failed replicas.

To Reproduce
Steps to reproduce the behavior:

1. Create a DR volume from a backup.
2. While DR is restoring, delete an instance-manager-r of one of the replica.
3. Wait for completion of the restore.
4. Now, DR volume has 1 failed replica and 3 healthy replicas.
5. Activate the DR volume.
6. Observe the DR volume state is not ready for workload.
7. Try to create PVC/PV using GUI, it fails saying level=error msg="Error in request: cannot create PV for standby volume

Expected behavior
On activation of the DR volume if the volume have one or more healthy replica, it should be ready for the workload.

Environment:

• Longhorn version: v1.2.1-rc1
• Installation method (e.g. Rancher Catalog App/Helm/Kubectl): kubectl