Since there is now a single consolidated RCU flavor, rcutorture needs to test extending of RCU readers via rcu_read_lock_bh() and rcu_read_lock_sched(). This commit adds this support, with added checks (just like for local_bh_enable()) to ensure that rcu_read_unlock_bh() will not be invoked while interrupts are disabled. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>