Temporarily disable multi-thread loop filter in cb4x4

The loop filter parameters change due to many experiments. The
multi-thread loop filter is built on certain assumptions that would
require changes in many table contents. Temporarily disable the
multi-thread loop filter pass and only maintain the single frame
reference during the development process.

Change-Id: I33a6a7a6fc4299f8fc414ae7f28c5a463af1e12b
4 files changed