sk-unix: Fix name resolving on nested mount points

In case if socket's cwd lays on nested mount point
we might resolve its path a bit incorrectly
(mount_resolve_path helper should not obtain
 paths with leading dot).

Thus send a path without leading dot for correct
name resolving.

Also add some error messages.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

sk-unix.c

@@ -229,7 +229,7 @@ static int resolve_rel_name(struct unix_sk_desc *sk, const struct fd_parms *p)
 		}
 
 		if ((st.st_ino == rel_name->udiag_vfs_ino) &&
-		    phys_stat_dev_match(st.st_dev, rel_name->udiag_vfs_dev, ns, path)) {
+		    phys_stat_dev_match(st.st_dev, rel_name->udiag_vfs_dev, ns, &path[1])) {
 			rel_name->dir = xstrdup(dir);
 			if (!rel_name->dir)
 				return -ENOMEM;