libvpx

Reduce loop filter in cyclic refresh.

Reduce the delta loop filter for blocks that are cyclicly refreshed.
This helps to reduce the dot artifacts that may happen
when zero_mv blocks are repeatedly loop-filtered.

This change, along with the fix in:
https://gerrit.chromium.org/gerrit/#/c/40409/
helps to reduce this artifact, but cannot remove the dot artifacts completely.

Change-Id: I44675e7a0f59295b648a3b7d4956fb301231a97f