title: Input/output error when writing to google cloud storage bucket
body: <p>I created a gcs bucket on <a href="https://console.cloud.google.com/storage/" rel="nofollow">https://console.cloud.google.com/storage/</a><br>
  and successfully mounted on an instance with gcsfuse,
  however, when I try to write to the mounted directory,  it shows an Input/output error.  </p>
  
  <pre><code>fuse_debug: Op 0x00000003        connection.go:395] &lt;- LookUpInode (parent 1, name "test")
  gcs: Req              0x1: &lt;- StatObject("test/")
  gcs: Req              0x2: &lt;- StatObject("test")
  gcs: Req              0x1: -&gt; StatObject("test/") (31.355698ms): gcs.NotFoundError: googleapi: Error 404: Not Found, notFound
  gcs: Req              0x2: -&gt; StatObject("test") (51.589538ms): gcs.NotFoundError: googleapi: Error 404: Not Found, notFound
  fuse_debug: Op 0x00000003        connection.go:476] -&gt; Error: "no such file or directory"
  fuse_debug: Op 0x00000004        connection.go:395] &lt;- MkDir (parent 1, name "test")
  gcs: Req              0x3: &lt;- CreateObject("test/")
  gcs: Req              0x3: -&gt; CreateObject("test/") (13.513239ms): googleapi: Error 403: Insufficient Permission, insufficientPermissions
  fuse_debug: Op 0x00000004        connection.go:476] -&gt; Error: "CreateChildDir: googleapi: Error 403: Insufficient Permission, insufficientPermissions"
  fuse: 2016/06/09 02:12:40.128885 *fuseops.MkDirOp error: CreateChildDir: googleapi: Error 403: Insufficient Permission, insufficientPermissions
  </code></pre>