Rollback

Rollback of the latest allocation changes on the minority of blobbers if the others are missing them

• Rollback means undoing the allocation changes ran on the minority of blobbers if it's not sycned by the majority of blobbers hosting the allocation.

• Rollback runs on an allocation if and only if the number of the blobbers on the latest version (having the latest changes) is less than the number of data shards of the allocations.

• Rollback occurs (if the check above if fulfilled) at the beginning of any allocation operation ran by gosdk or zboxcli, given MultiOperation is enabled.