Packer build configuration - hangs during shell provisioning after a reboot

centos7-vagrant.json

{
  "variables": {
    "iso_checksum": "27bd866242ee058b7a5754e83d8ee8403e216b93d130d800852a96f41c34d86a",
    "iso_checksum_type": "sha256",
    "iso_name": "CentOS-7-x86_64-Minimal-1611",
    "iso_url": "http://mirror.cs.vt.edu/pub/CentOS/7/isos/x86_64/CentOS-7-x86_64-Minimal-1611.iso",
    "ssh_password": "vagrant",
    "ssh_username": "vagrant",
    "scripts_dir" : "scripts",
    "version": "0.0.1"
  },
  "builders": [
    {
      "boot_command": [
        "<wait><esc><esc>",
        "linux ks=http://{{.HTTPIP}}:{{.HTTPPort}}/centos7.ks<enter>"
      ],
      "boot_wait": "10s",
      "guest_additions_path": "VBoxGuestAdditions_{{.Version}}.iso",
      "guest_os_type": "RedHat_64",
      "headless": false,
      "http_directory": "http",
      "iso_checksum": "{{ user `iso_checksum` }}",
      "iso_checksum_type": "{{ user `iso_checksum_type` }}",
      "iso_url": "{{ user `iso_url` }}",
      "shutdown_command": "sudo -S shutdown -P now",
      "ssh_password": "{{ user `ssh_password` }}",
      "ssh_port": 22,
      "ssh_username": "{{ user `ssh_username` }}",
      "ssh_timeout": "10m",
      "type": "virtualbox-iso",
      "vboxmanage": [
        [
          "modifyvm",
          "{{.Name}}",
          "--memory",
          "2048"
        ],
        [
          "modifyvm",
          "{{.Name}}",
          "--cpus",
          "2"
        ]
      ],
      "virtualbox_version_file": ".vbox_version",
      "vm_name": "centos7-box"
    }
  ],
  "provisioners": [
    {
      "override": {
        "virtualbox-iso": {
          "execute_command": "echo 'vagrant'|sudo -S bash '{{.Path}}'"
        }
      },
      "expect_disconnect": true,
      "scripts": [
        "{{user `scripts_dir`}}/update.sh",
        "{{user `scripts_dir`}}/base.sh",
        "{{user `scripts_dir`}}/vagrant.sh",
        "{{user `scripts_dir`}}/virtualbox.sh",
        "{{user `scripts_dir`}}/cleanup.sh"
      ],
      "start_retry_timeout": "2m",
      "type": "shell"
    }
  ],
  "post-processors": [
    {
      "output": "./box/{{.Provider}}/{{user `iso_name`}}-{{user `version`}}.box",
      "type": "vagrant"
    }
  ]
}

centos7.ks

lang en_US.UTF-8
keyboard us
rootpw --plaintext vagrant --lock
authconfig --enableshadow --passalgo=sha512
timezone Etc/UTC --isUtc

install
cdrom
network --onboot yes --bootproto=dhcp --device=enp0s3 --noipv6 --activate
firewall --enabled --service=ssh
selinux --disabled
bootloader --location=mbr --driveorder=sda --append="crashkernel=auto rhgb quiet"
text
skipx
zerombr
clearpart --all --initlabel
autopart
firstboot --disabled
user --name=vagrant --groups=wheel --password=vagrant
reboot

%packages
@^minimal
@core
sudo
%end

%post
/bin/cat << EOF > /etc/sudoers.d/wheel
Defaults:%wheel env_keep += "SSH_AUTH_SOCK"
Defaults:%wheel !requiretty
%wheel ALL=(ALL) NOPASSWD:ALL
EOF
/bin/chmod 0440 /etc/sudoers.d/wheel
/bin/echo 'UseDNS no' >> /etc/ssh/sshd_config
%end

packer.log

2017/03/19 17:43:02 ui:     virtualbox-iso: python-firewall.noarch 0:0.4.3.2-8.1.el7_3.2
2017/03/19 17:43:02 ui:     virtualbox-iso: python-perf.x86_64 0:3.10.0-514.10.2.el7
2017/03/19 17:43:02 ui:     virtualbox-iso: selinux-policy.noarch 0:3.13.1-102.el7_3.15
2017/03/19 17:43:02 ui:     virtualbox-iso: selinux-policy-targeted.noarch 0:3.13.1-102.el7_3.15
2017/03/19 17:43:02 ui:     virtualbox-iso: sudo.x86_64 0:1.8.6p7-21.el7_3
2017/03/19 17:43:02 ui:     virtualbox-iso: systemd.x86_64 0:219-30.el7_3.7
2017/03/19 17:43:02 ui:     virtualbox-iso: systemd-libs.x86_64 0:219-30.el7_3.7
2017/03/19 17:43:02 ui:     virtualbox-iso: systemd-sysv.x86_64 0:219-30.el7_3.7
2017/03/19 17:43:02 ui:     virtualbox-iso: tuned.noarch 0:2.7.1-3.el7_3.1
2017/03/19 17:43:02 ui:     virtualbox-iso: tzdata.noarch 0:2017a-1.el7
2017/03/19 17:43:02 ui:     virtualbox-iso: vim-minimal.x86_64 2:7.4.160-1.el7_3.1
2017/03/19 17:43:02 ui:     virtualbox-iso: wpa_supplicant.x86_64 1:2.0-21.el7_3
2017/03/19 17:43:02 ui:     virtualbox-iso: xfsprogs.x86_64 0:4.5.0-9.el7_3
2017/03/19 17:43:02 ui:     virtualbox-iso:
2017/03/19 17:43:02 ui:     virtualbox-iso: Complete!
2017/03/19 17:43:02 ui:     virtualbox-iso: Rebooting the machine...
2017/03/19 17:50:50 packer: 2017/03/19 17:50:50 Received interrupt signal (count: 1). Ignoring.
2017/03/19 17:50:50 packer: 2017/03/19 17:50:50 Received interrupt signal (count: 1). Ignoring.
2017/03/19 17:50:50 packer: 2017/03/19 17:50:50 Received interrupt signal (count: 1). Ignoring.
2017/03/19 17:50:50 Stopping build: virtualbox-iso

update.sh

#!/bin/bash

echo "==> Applying updates"
yum -y update

# Reboot
echo "Rebooting the machine..."
systemctl stop network
shutdown -r now
sleep 60

hello,I came into the same problem, what is your final solution about rebooting?