Btrfs-progs: mkfs: make sure we can deal with hard links with -r option

Btrfs-progs: mkfs: make sure we can deal with hard links with -r option

Steps to reproduce:
 # mkdir -p /tmp/test
 # touch /tmp/test/file
 # ln /tmp/test/file /tmp/test/hardlinks
 # mkfs.btrfs -f /dev/sda13 -r /tmp/test
 # btrfs check /dev/sda13

To deal with hard link, we must deal with inode with same inode id rather
than increase inode id by ourselves.

Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>