rcutorture: Default to grace-period-initialization delays

Given that CPU-hotplug events are now applied only at the starts of
grace periods, it makes sense to unconditionally enable slow grace-period
initialization for rcutorture testing.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

lib/Kconfig.debug

@@ -1276,7 +1276,7 @@ config RCU_TORTURE_TEST_SLOW_INIT
 config RCU_TORTURE_TEST_SLOW_INIT_DELAY
 	int "How much to slow down RCU grace-period initialization"
 	range 0 5
-	default 0
+	default 3
 	help
 	  This option specifies the number of jiffies to wait between
 	  each rcu_node structure initialization.