rcutorture: Set KCSAN Kconfig options to detect more data races

This commit enables the KCSAN Kconfig options that (1) detect data
races between reads and writes even when the writes do not change the
variable's value and (2) detect data races involving plain C-language
writes.  These changes only affect scripted rcutorture runs and can be
overridden using the kvm.sh --kconfig argument.

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