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