Merge pull request #5312 from xinxinsh/wip-sparse-copy

use SEEK_HOLE/SEEK_DATA for sparse copy

Reviewed-by: Haomai Wang <haomaiwang@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>
Reviewed-by: Kefu Chai <kchai@redhat.com>

diff --cc src/os/FileStore.cc
Simple merge

diff --cc src/os/FileStore.h
Simple merge