Add retries to ceph-deploy gatherkeys

During heavy load sometimes ceph-deploy gatherkeys
fails on the first request with connection issues.
Adding a retry will avoid race conditions from
breaking deployment.

Change-Id: I077ef2019d7796ce1fe4510afae806f359e5a0e1
Partial-Bug: #1398096
Merge "Add retries to ceph-deploy gatherkeys"