torture: Make kvm.sh include --kconfig arguments in CPU calculation

Currently, passing something like "--kconfig CONFIG_NR_CPUS=2" to kvm.sh
has no effect on scenario scheduling.  For scenarios that do not specify
the number of CPUs, this can result in kvm.sh wastefully scheduling only
one scenario at a time even when the --kconfig argument would allow
a number to be run concurrently.  This commit therefore makes kvm.sh
consider the --kconfig arguments when scheduling scenarios across the
available CPUs.

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