Fix an uninitialized memory error in EvaluationCallbackTest

prepare_parameter_hash was being used uninitialized.

Change-Id: Ia1a2e2da6845dc536f5463fe12d4ffcd58a95f8c

internal/ceres/evaluation_callback_test.cc

diff --git a/internal/ceres/evaluation_callback_test.cc b/internal/ceres/evaluation_callback_test.cc
index cec88d6..a28d5a8 100644
--- a/internal/ceres/evaluation_callback_test.cc
+++ b/internal/ceres/evaluation_callback_test.cc
@@ -66,6 +66,9 @@
       : EvaluationCallback(),
         user_parameter_block(parameter),
         prepare_num_calls(0),
+        prepare_requested_jacobians(false),
+        prepare_new_evaluation_point(false),
+        prepare_parameter_hash(kUninitialized),
         evaluate_num_calls(0),
         evaluate_last_parameter_hash(kUninitialized) {}