mxgrub: Specify init command on Linux Kernel command line

With [merge/pull request bee-files#624][1] the command line for init is
now longer hard coded into the configuration of the Linux Kernel. So
specify in the GRUB configuration.

Later `/bin/systemd` should be changed to `/lib/systemd/systemd`.

[1]: mariux64/bee-files#624

mxgrub/mxgrub

@@ -233,7 +233,7 @@ sub update_grub_cfg {
 
 	for my $label (@MARIUX) {
 		my $image=label_to_image($label);
-		$kernellist.="\tmenuentry \"$label\" --unrestricted { save_env chosen ; linux /boot/$image crashkernel=256M root=LABEL=root ro console=ttyS1,115200n8 console=tty0 ; initrd /boot/grub/initramfs.igz }\n";
+		$kernellist.="\tmenuentry \"$label\" --unrestricted { save_env chosen ; linux /boot/$image crashkernel=256M root=LABEL=root ro console=ttyS1,115200n8 console=tty0 init=/bin/systemd ; initrd /boot/grub/initramfs.igz }\n";
 	}
 
 	my $GRUB_CFG_NEW=<<"EOF";
@@ -247,10 +247,10 @@ set default="$MARIUX_DEFAULT"
 load_env
 if [ -e /etc/local/USB.usb ]; then
 	set default="mariuxUSB"
-	menuentry "mariuxUSB" --unrestricted { save_env chosen ; linux /boot/bzImage.x86_64 crashkernel=256M root=LABEL=rootusb ro ; initrd /boot/grub/initramfs.igz }
+	menuentry "mariuxUSB" --unrestricted { save_env chosen ; linux /boot/bzImage.x86_64 crashkernel=256M root=LABEL=rootusb ro init=/bin/systemd ; initrd /boot/grub/initramfs.igz }
 else
 
-menuentry "$MARIUX_DEFAULT" --unrestricted { set chosen="$submenu>$MARIUX_DEFAULT" ; save_env chosen ; linux /boot/bzImage.x86_64 crashkernel=256M root=LABEL=root ro console=ttyS1,115200n8 console=tty0 ; initrd /boot/grub/initramfs.igz }
+menuentry "$MARIUX_DEFAULT" --unrestricted { set chosen="$submenu>$MARIUX_DEFAULT" ; save_env chosen ; linux /boot/bzImage.x86_64 crashkernel=256M root=LABEL=root ro console=ttyS1,115200n8 console=tty0 init=/bin/systemd ; initrd /boot/grub/initramfs.igz }
 
 submenu "$submenu" --unrestricted {
 $kernellist