rcutorture: Add rcutree.use_softirq=0 to RUDE01 and TASKS01

RCU's rcutree.use_softirq=0 kernel boot parameter substitutes the per-CPU
rcuc kthreads for softirq, which is used in real-time installations.
However, none of the rcutorture scenarios test this parameter.
This commit therefore adds rcutree.use_softirq=0 to the RUDE01 and
TASKS01 rcutorture scenarios, both of which indirectly exercise RCU.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>