torture: Use mktemp instead of guessing at unique names

This commit drags the rcutorture scripting kicking and screaming into the
twenty-first century by making use of the BSD-derived mktemp command to
create temporary files and directories. In happy contrast to many of its
ill-behaved predecessors, mktemp seems to actually work reasonably reliably!

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

torture: Make kvm-test-1-run-batch.sh select per-scenario affinity masks

This commit causes kvm-test-1-run-batch.sh to use the new
kvm-assign-cpus.sh and kvm-get-cpus-script.sh scripts to create a
TORTURE_AFFINITY environment variable containing either an empty string
(for no affinity) or a list of CPUs to pin the scenario's vCPUs to.
The additional change to kvm-test-1-run.sh places the per-scenario
number-of-CPUs information where it can easily be found.

If there is some reason why affinity cannot be supplied, this commit
prints and logs the reason via changes to kvm-again.sh.

Finally, this commit updates the kvm-remote.sh script to copy the
qemu-affinity output files back to the host system.

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

torture: Make kvm.sh select per-scenario affinity masks

This commit causes kvm.sh to use the new kvm-assign-cpus.sh and
kvm-get-cpus-script.sh scripts to create a TORTURE_AFFINITY environment
variable containing either an empty string (for no affinity) or a list
of CPUs to pin the scenario's vCPUs to. A later commit will make
use of this information to actually pin the vCPUs.

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

torture: Add kvm-again.sh to rerun a previous torture-test

This commit adds a kvm-again.sh script that, given the results directory
of a torture-test run, re-runs that test. This means that the kernels
need not be rebuilt, but it also is a step towards running torture tests
on remote systems.

This commit also adds a kvm-test-1-run-batch.sh script that runs one
batch out of the torture test. The idea is to copy a results directory
tree to remote systems, then use kvm-test-1-run-batch.sh to run batches
on these systems.

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