fix error directory of fluid inference unitest

Author: luotao1

paddle/fluid/inference/tests/book/CMakeLists.txt

@@ -4,7 +4,7 @@ function(inference_test TARGET_NAME)
   set(multiValueArgs ARGS)
   cmake_parse_arguments(inference_test "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})
 
-  set(PYTHON_TESTS_DIR ${PADDLE_SOURCE_DIR}/python/paddle/v2/fluid/tests)
+  set(PYTHON_TESTS_DIR ${PADDLE_SOURCE_DIR}/python/paddle/fluid/tests)
   set(arg_list "")
   if(inference_test_ARGS)
     foreach(arg ${inference_test_ARGS})