Change encoder initialization in unit tests

In some unit tests, the set control is done when video->frame() is 1.
Modified it so that the config initialization was done before encoding
frames.

Change-Id: I698b17b518fec64275f23cec68cf51bd8b60a716
diff --git a/test/active_map_test.cc b/test/active_map_test.cc
index a2b0546..0f8a732 100644
--- a/test/active_map_test.cc
+++ b/test/active_map_test.cc
@@ -37,7 +37,7 @@
 
   virtual void PreEncodeFrameHook(::libaom_test::VideoSource *video,
                                   ::libaom_test::Encoder *encoder) {
-    if (video->frame() == 1) {
+    if (video->frame() == 0) {
       encoder->Control(AOME_SET_CPUUSED, cpu_used_);
     } else if (video->frame() == 3) {
       aom_active_map_t map = aom_active_map_t();