Add a test vector for loopfilter

Add a test vector for loopfilter

The test vector exercises the loopfilter behavior at frame boundary.

blue_sky_1080p25.y4m --good --cpu-used=2 --threads=0 --profile=0
--lag-in-frames=25 --limit=300 --min-q=0 --max-q=63 --cq-level=20
--end-usage=0 --auto-alt-ref=1 -p 2 --kf-max-dist=9999 --kf-min-dist=0
--drop-frame=0 --static-thresh=0 --bias-pct=50 --minsection-pct=0
--maxsection-pct=2000 --arnr-maxframes=7 --arnr-strength=5
--arnr-type=3 --sharpness=0 --undershoot-pct=100 --target-bitrate=6000

Change-Id: Ibd0807395d2fe87f24f81f990369678df3de7c23