rcutorture: Make scenario TREE04 enable lazy call_rcu()

This commit enables the RCU_LAZY Kconfig option in scenario TREE04 in
order to provide some ongoing testing of this configuration.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>