nf: xt_qtaguid: fix handling for cases where tunnels are used.

* fix skb->dev vs par->in/out
When there is some forwarding going on, it introduces extra state
around devs associated with xt_action_param->in/out and sk_buff->dev.
E.g.
   par->in and par->out are both set, or
   skb->dev and par->out are both set (and different)
This would lead qtaguid to make the wrong assumption about the
direction and update the wrong device stats.
Now we rely more on par->in/out.

* Fix handling when qtaguid is used as "owner"
When qtaguid is used as an owner module, and sk_socket->file is
not there (happens when tunnels are involved), it would
incorrectly do a tag stats update.

* Correct debug messages.

Bug: 11687690
Change-Id: I2b1ff8bd7131969ce9e25f8291d83a6280b3ba7f
Signed-off-by: JP Abgrall <jpa@google.com>