Merge branch 'ipsec: fix splat due to ipcomp fallback tunnel'

Sabrina Dubroca says:

====================
IPcomp tunnel states have an associated fallback tunnel, a keep a
reference on the corresponding xfrm_state, to allow deleting that
extra state when it's not needed anymore. These states cause issues
during netns deletion.

Commit f75a2804 ("xfrm: destroy xfrm_state synchronously on net
exit path") tried to address these problems but doesn't fully solve
them, and slowed down netns deletion by adding one synchronize_rcu per
deleted state.

The first patch solves the problem by moving the fallback state
deletion earlier (when we delete the user state, rather than at
destruction), then we can revert the previous fix.
====================

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>