Add timeout to Ceph GET API calls

This is to add neccessary changes in go-ceph to handle the ceph-csi issue #ceph/ceph-csi#3657.

Provide a way to configure the timeout for the ceph Get API calls to avoid command stuck if there is some problem between the ceph cluster and the csi driver (cluster health, slow ops, or short network connectivity problem)

For more info please refer to the ceph-csi issue.