Currently, in CONFIG_RCU_BOOST kernels, if the rcu_torture_init() function's call to cpuhp_setup_state() fails, rcu_torture_cleanup() gamely passes nonsense to cpuhp_remove_state(). This results in strange and misleading splats. This commit therefore ensures that if the rcu_torture_init() function's call to cpuhp_setup_state() fails, rcu_torture_cleanup() avoids invoking cpuhp_remove_state(). Signed-off-by: Paul E. McKenney <paulmck@kernel.org>