torture: Make upper-case-only no-dot no-slash scenario names official

This commit enforces the defacto restriction on scenario names, which is
that they contain neither "/", ".", nor lowercase alphabetic characters.
This restriction avoids collisions between scenario names and the torture
scripting's files and directories.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/testing/selftests/rcutorture/bin/kvm.sh

@@ -104,7 +104,7 @@ do
 		TORTURE_BUILDONLY=1
 		;;
 	--configs|--config)
-		checkarg --configs "(list of config files)" "$#" "$2" '^[^/]\+$' '^--'
+		checkarg --configs "(list of config files)" "$#" "$2" '^[^/.a-z]\+$' '^--'
 		configs="$configs $2"
 		shift
 		;;