The call to commonOp.Logf in sendBazilfuseResponse is extremely hot for
allocations, presumably because it needs to allocate an argument slice.
It is normally not needed at all, so why pay for it?

This saves an allocation that is very much on the hot path in a
read-heavy load.

For GoogleCloudPlatform/gcsfuse#89.

This was a cute hack, but I haven't used it in awhile, and it won't work
(for gcsfuse at least) as of the changes for
GoogleCloudPlatform/gcsfuse#89.

For GoogleCloudPlatform/gcsfuse#81.