This option is unused and is likely going to confuse
deployers, especially when using the share usage size
tracking feature with a similarly named option
(share_usage_size_update_interval) [1].
We can remove this option in the Train release.
Closes-Bug: #1813054
[1] https://review.openstack.org/#/c/465055/
Change-Id: Id4585fa887e5bdfd5743dad2c490392ba0401061