Fix valgrind warning
Fix valgrind warning

This commit adds initialization for tmp_rd_stats, to resolve valgrind
warning of "Conditional jump or move depends on uninitialised value"

Change-Id: I79ed3bc046a66457c27185782645938d223872ba

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