btrfs: test fsync after hole punching when using the no-holes feature

btrfs: test fsync after hole punching when using the no-holes feature

Test that when we have the no-holes feature enabled and a specific
metadata layout, if we punch a hole that starts at file offset 0 and
fsync the file, after replaying the log the hole exists.

This currently fails on btrfs but is fixed by a patch for the linux
kernel with the following subject:

 "Btrfs: fix missing hole after hole punching and fsync when using NO_HOLES"

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>