When using ipv6, the IP address must be enclosed in square brackets
according to RFC 3986, Section 3.2.2. Without this, an ipv6 cloud will
fail to connect to the ceph cluster prior to backup because the address
and port are not parsed correctly.
Closes-Bug: #1640914
Change-Id: I6501c7cdac38fe545d12e786448a8e0c0a4f6a25