The URI syntax is consistent with the NBD and Gluster syntax.  The
syntax is

  sheepdog[+tcp]://[host:port]/vdiname[#snapid|#tag]
Signed-off-by: NMORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>