Block align start and length while punching holes

If hole punching offset is within block, kernel will write
zeros forcefully. Block align offset and length used for punching
to avoid unnecessary write to the disk while punching.

Test: acloud delete --all && m && acloud create --local-instance --local-image && adb logcat -c && m FileSystemUtilsTests && atest -c FileSystemUtilsTests
Bug: 301631861
Change-Id: Ib65e4fb9419125e89e9253bec769fce53304649a