title: Virtualbox + shared folder gives protocol error for user with group access vboxsf
body: <p>I have installed virtualbox Ubuntu 16.04 LTS - 64bit server on my windows 10 machine.
  Installation went just fine. 
  However, now I am trying to get git clone from my existing repo to the shared folder "sf_Users" in this case, it keeps on giving error as </p>
  
  <pre><code>fatal: could not create work tree dir 'application': Protocol error
  
  My VM settings -&gt; shared folders -&gt; machine folder says =&gt; Users C:/Users/app-dev
   -- auto-mount = Yes -- Access = Full
  </code></pre>
  
  <p>from terminal my id shows up access to group vboxsf</p>
  
  <pre><code>dev@app-dev:/media/sf_Users$ id
  uid=1000(dev) gid=1000(dev) groups=1000(dev),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),110(lxd),119(libvirtd),120(lpadmin),121(sambashare),125(vboxsf)
  dev@app-dev:/media/sf_Users$ cd ..
  dev@app-dev:/media$ ls -al
  total 12
  drwxr-xr-x  4 root root   4096 Nov 29  2016 .
  drwxr-xr-x 23 root root   4096 Nov 29 10:04 ..
  drwxr-xr-x  2 root root   4096 Nov 29 09:59 cdrom
  drwxrwx---  1 root vboxsf    0 Nov 28 09:20 sf_Users
  </code></pre>
  
  <p>from "id" command, I know that I have access to vboxsf. Am i missing something more?</p>