rcu: prevent console flood when one CPU sees another AWOL via RCU

One small change needed to keep from flooding the console when one
CPU notices that another is AWOL.  Unless I am missing something subtle.
Otherwise the cleanups look good!

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>