Cherry-pick Daala b5020bee:
 Remove redundant test in od_ec_decode_bool_q15().
Using a test that decodes 100M random binary symbols, making this change
 produced a speed up of 8.81% with gcc-4.9.3 and 3.71% with clang-3.7.1,
 both compiled with -O2.

Change-Id: If6d0077a56121a575ae53bcd4d1d9b7d800a317d