See the documentation on MountConfig.DisableWritebackCaching for
discussion.

We can't do this now that the kernel chooses mtimes and sends setattr
requests due to our use of writeback caching.

Otherwise we get confusing EOF errors when we later call out to osxfuse.

Doing so adds lots of visual clutter.

Allowing the kernel to send multiple reads for the same file handle
concurrently interferes with sequential read detection like that in
GoogleCloudPlatform/gcsfuse#103.

One of them caused the writeMessage error observed on OS X in
GoogleCloudPlatform/gcsfuse#101.

It's not expecting them.

This reproduces the writeMessage errors from
GoogleCloudPlatform/gcsfuse#101.