VSA does not release storage on thin provisoned backup repo using trim

[Spex]

As part of a support ticket (case # 08231420), we discovered that VSA does not support thin provisioning.
The problem is that neither fstrim nor fstab with the discard option are used.

Since the size of a repository volume cannot currently be changed, a generous initial size must be chosen.
This is particularly problematic when SOBR is not the optimal solution.

Therefore, please consider this minor change in the next release.