toolbox: go back to fedora:latest

With systemd v233, the nspawn SIGKILL problems appear to be fixed.

There is also an image on Docker Hub for aarch64 now, so use it.
diff --git a/toolbox b/toolbox
index 7a74436..c7be171 100755
--- a/toolbox
+++ b/toolbox
@@ -7,12 +7,12 @@
 
 case ${machine} in
 	aarch64 )
-		TOOLBOX_NAME=fedora-base-24-1.1.aarch64
-		TOOLBOX_DOCKER_ARCHIVE="https://dl.fedoraproject.org/pub/fedora-secondary/releases/24/Docker/aarch64/images/Fedora-Docker-Base-24-1.1.aarch64.tar.xz"
+		TOOLBOX_DOCKER_IMAGE=aarch64/fedora
+		TOOLBOX_DOCKER_TAG=latest
 		;;
 	x86_64 )
 		TOOLBOX_DOCKER_IMAGE=fedora
-		TOOLBOX_DOCKER_TAG=24
+		TOOLBOX_DOCKER_TAG=latest
 		;;
 	* )
 		echo "Warning: Unknown machine type ${machine}" >&2