Fix constructor order in unit tests (sanitizer)

The WithParamTest constructor needs to be called first, as the
EncoderTest constructor is called with 'GET_PARAM'.

BUG=aomedia:580

Change-Id: I17f3c02c0a0eec103fb3505301b5eb6dfdef851c
diff --git a/test/datarate_test.cc b/test/datarate_test.cc
index a4a6826..6a1b4e1 100644
--- a/test/datarate_test.cc
+++ b/test/datarate_test.cc
@@ -21,8 +21,8 @@
 namespace {
 
 class DatarateTestLarge
-    : public ::libaom_test::EncoderTest,
-      public ::libaom_test::CodecTestWith2Params<libaom_test::TestMode, int> {
+    : public ::libaom_test::CodecTestWith2Params<libaom_test::TestMode, int>,
+      public ::libaom_test::EncoderTest {
  public:
   DatarateTestLarge() : EncoderTest(GET_PARAM(0)) {}