rcutorture: Run rcu_torture_writer at normal priority

There are usually lots of readers and only one writer, so if there has
to be a choice, we would want rcu_torture_writer to win.  This commit
therefore removes the set_user_nice() from rcu_torture_writer().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

kernel/rcu/rcutorture.c

@@ -758,7 +758,6 @@ rcu_torture_writer(void *arg)
 	int nsynctypes = 0;
 
 	VERBOSE_TOROUT_STRING("rcu_torture_writer task started");
-	set_user_nice(current, MAX_NICE);
 
 	/* Initialize synctype[] array.  If none set, take default. */
 	if (!gp_cond1 && !gp_exp1 && !gp_normal1 && !gp_sync)