Initialize motion vector cost
Initialize motion vector cost

Make av1_initialize_rd_consts() initialize motion vector cost
values consistently.

BUG=aomedia:91

Change-Id: I6524d3fc73281d2c78962062803acac0ce71e87c

smarter/aom,GrokImageCompression/aom,mbebenita/aom,luctrudeau/aom,smarter/aom,GrokImageCompression/aom,mbebenita/aom,smarter/aom,smarter/aom,mbebenita/aom,mbebenita/aom,smarter/aom,mbebenita/aom,GrokImageCompression/aom,luctrudeau/aom,GrokImageCompression/aom,mbebenita/aom,luctrudeau/aom,luctrudeau/aom,GrokImageCompression/aom,mbebenita/aom,luctrudeau/aom,mbebenita/aom,smarter/aom,luctrudeau/aom,GrokImageCompression/aom,mbebenita/aom