fix a VirtualBox bug related to “sendfile”

http://docs-v1.vagrantup.com/v1/docs/config/vm/share_folder.html
There is a VirtualBox bug related to “sendfile” which can result in corrupted or non-updating files. You should disable “sendfile” in any web servers you have running.

In Nginx:

sendfile off;
In Apache:

EnableSendfile Off