Update vagrant centos config to CentOS 7.4

Change-Id: I45c1227b53ba9e57b94f1bc68de939cd3ce9d619
Signed-off-by: Dave Wallace <dwallacelf@gmail.com>
diff --git a/extras/vagrant/Vagrantfile.vcl_test b/extras/vagrant/Vagrantfile.vcl_test
index 92d6832..d055942 100644
--- a/extras/vagrant/Vagrantfile.vcl_test
+++ b/extras/vagrant/Vagrantfile.vcl_test
@@ -6,7 +6,8 @@
   # Pick the right distro and bootstrap, default is ubuntu1604
   distro = ( ENV['VPP_VAGRANT_DISTRO'] || "ubuntu1604")
   if distro == 'centos7'
-    config.vm.box = "puppetlabs/centos-7.2-64-nocm"
+    config.vm.box = "centos/7"
+    config.vm.box_version = "1708.01"
     config.ssh.insert_key = false
   else
     config.vm.box = "puppetlabs/ubuntu-16.04-64-nocm"