btrfs-progs: fix return value problem for btrfs sub show

If you exec:
	# btrfs sub show <dir>	<== non-subvolume dir
The cmd print error messages as expected, but returns 0.
By convetion, it should return non-zero and we should explicitly
set it before it goto out.

With other pieces adopted:
1) removed a unnecessary return value set -EINVAL
2) fixed another code branch which may return 0 upon error.
3) with 2) applied, the ret = 0 follows can be removed

Signed-off-by: Gui Hecheng <guihc.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
btrfs-progs: apply realpath for btrfs fi show when mount point is given

For now,
	# btrfs fi show /mnt/btrfs
gives info correctly, while
	# btrfs fi show /mnt/btrfs/
gives nothing.

This implies that the @realpath() function should be applied to
unify the behavior.

Made a more clear comment right above the call as well.

Signed-off-by: Gui Hecheng <guihc.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
Btrfs-progs: add_refs_for_implied: Use root_id instead of root_bytenr.

resolve_one_root() returns the objectid of a tree rather than the logical
address of the root node. Hence using root_bytenr is misleading. Fix this.

Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: David Sterba <dsterba@suse.cz>