Automatic merge from submit-queue (batch tested with PRs 39625, 39842)

AWS: Remove duplicate calls to DescribeInstance during volume operations

This change removes all duplicate calls to describeInstance
from aws volume code path.

**What this PR does / why we need it**:

This PR removes the duplicate calls present in disk check code paths in AWS. I can confirm that `getAWSInstance` actually returns all instance information already and hence there is no need of making separate `describeInstance` call.

Related to - https://github.com/kubernetes/kubernetes/issues/39526

cc @justinsb @jsafrane