xfrm: Refcount destination entry on xfrm_lookup

xfrm: Refcount destination entry on xfrm_lookup

BugLink: http://bugs.launchpad.net/bugs/769042

[ Upstream commit fbd5060875d25f7764fd1c3d35b83a8ed1d88d7b ]

We return a destination entry without refcount if a socket
policy is found in xfrm_lookup. This triggers a warning on
a negative refcount when freeeing this dst entry. So take
a refcount in this case to fix it.

This refcount was forgotten when xfrm changed to cache bundles
instead of policies for outgoing flows.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Acked-by: Timo Teräs <timo.teras@iki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Leann Ogasawara <leann.ogasawara@canonical.com>