Move NEWMV check code to USE_DISCOUNT_NEWMV_TEST
Move NEWMV check code to USE_DISCOUNT_NEWMV_TEST

The NEWMV rate cost is not precise only when
USE_DISCOUNT_NEWMV_TEST is on

STATS_CHANGED about 0.02%

Change-Id: I8d64ce785cfc83962ea486e0d47f4dcc693f3de8

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom