Change name of thread_pool files to fixed_size_thread_pool when
appropriate
diff --git a/test/cpp/end2end/mock_test.cc b/test/cpp/end2end/mock_test.cc
index 0cffaf6..0da42fc 100644
--- a/test/cpp/end2end/mock_test.cc
+++ b/test/cpp/end2end/mock_test.cc
@@ -42,13 +42,13 @@
 #include <grpc++/client_context.h>
 #include <grpc++/create_channel.h>
 #include <grpc++/credentials.h>
+#include <grpc++/fixed_size_thread_pool.h>
 #include <grpc++/server.h>
 #include <grpc++/server_builder.h>
 #include <grpc++/server_context.h>
 #include <grpc++/server_credentials.h>
 #include <grpc++/status.h>
 #include <grpc++/stream.h>
-#include <grpc++/thread_pool.h>
 #include <grpc++/time.h>
 #include <gtest/gtest.h>