Don't install busybox any longer by default

busybox is useful for debugging initramfs issues, though it's not
necessary by default. Also tools like cryptsetup which rely on busybox
in initramfs stage have busybox as dependency anyways.

Thanks: Patrick Schleizer + Chris Hofstaedtler
Closes: #240

chroot-script

@@ -349,8 +349,7 @@ kernel() {
   $APTUPDATE
   KVER=$(get_kernel_version)
   if [ -n "$KVER" ] ; then
-     # note: install busybox to be able to debug initramfs
-     KERNELPACKAGES="linux-image-$KVER linux-headers-$KVER busybox firmware-linux-free $INITRD_GENERATOR"
+     KERNELPACKAGES="linux-image-$KVER linux-headers-$KVER firmware-linux-free $INITRD_GENERATOR"
      # only add firmware-linux if we have non-free as a component
      if expr "$COMPONENTS" : '.*non-free' >/dev/null ; then
        KERNELPACKAGES="$KERNELPACKAGES firmware-linux"