rcutorture: Move common qemu flags to kvm-test-1.sh

Currently, most qemu flags are calculated in kvm-test-1-rcu.sh,
except that -nographics is set up by kvm.sh.  This commit promotes
one-stop shopping by consolidating the determination of qemu flags into
kvm-test-1-rcu.sh.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>