Revert "rcu: Add RCU type to callback-invocation tracing"

This reverts commit fce8999b87ede31087720a6509e9ae198eefa036.
Revert "rcu: Don't destroy rcu_torture_boost() callback until it is done"

This reverts commit 06bea3981abe53409efd0a8c73c01a3c9f49e8a5.