Add a retry loop to ensure the dataset being renamed
is cleanly unmounted before the rename operation.
Change-Id: Ie506f237010c415ee9f0d64abbefd5854f776a5f
Closes-Bug: #1785180
(cherry picked from commit d7c01efb44)
(cherry picked from commit 6d8f47d3c3)
(cherry picked from commit 820638ccef)