btrfs-progs: Fix the return value when executing 'btrfs prop get' on an uncompressed...

btrfs-progs: Fix the return value when executing 'btrfs prop get' on an uncompressed file

When executing 'btrfs prop get' on a file which is not compressed, return
value will always be 50 since prop_compress() return -ENOATTR.

But the codes have already check the errno to avoid unnecessary error
message, so the return value should also set to 0.

Signed-off-by: Qu Wenruo <quwenro@cn.fujitsu.com>
Reviewed-by: Filipe Manana <fdmanana@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.cz>