Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Added PV GET api rule to external-provisioner

Adds the PV GET API rule to the system:external-provisioner cluster role. It is required because the provisioner does a GET here:
https://github.com/kubernetes-incubator/external-storage/blob/master/lib/controller/controller.go#L1121

Fixes #65058

/sig storage
/kind bug
/priority critical-urgent
/cc @msau42 @sbezverk 

```release-note
NONE
```