Rename batch->op in skiaserve

Change-Id: Ib831b9a6bcf4f37c0f077b26f68b1cefef81bb73
Reviewed-on: https://skia-review.googlesource.com/6351
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
9 files changed