vagrant: disable automatic update on start

The box update requires an internet connection.
It is better to disable it on vagrant start.
It still can be updated with the manual command:
	vagrant box update

Change-Id: I04e05ea08477bf36f25672c54d0a057d995d4a42
Signed-off-by: Thomas Monjalon <thomas.monjalon@6wind.com>
diff --git a/build-root/vagrant/Vagrantfile b/build-root/vagrant/Vagrantfile
index 06063e3..7067bfc 100644
--- a/build-root/vagrant/Vagrantfile
+++ b/build-root/vagrant/Vagrantfile
@@ -10,6 +10,7 @@
   else
     config.vm.box = "puppetlabs/ubuntu-14.04-64-nocm"
   end
+  config.vm.box_check_update = false
 
   config.vm.provision :shell, :path => File.join(File.dirname(__FILE__),"update.sh")
   config.vm.provision :shell, :path => File.join(File.dirname(__FILE__),"build.sh"), :args => "/vpp vagrant"