Refactor tests a bit to reduce code duplication.

(Still needs more work).

Change-Id: I164c206ab0deb354c3298ee00b6570e9180c4f56
diff --git a/google_keymaster.cpp b/google_keymaster.cpp
index 582a03b..f34d1ea 100644
--- a/google_keymaster.cpp
+++ b/google_keymaster.cpp
@@ -243,6 +243,9 @@
 
 void GoogleKeymaster::UpdateOperation(const UpdateOperationRequest& request,
                                       UpdateOperationResponse* response) {
+    if (response == NULL)
+        return;
+
     OpTableEntry* entry = FindOperation(request.op_handle);
     if (entry == NULL) {
         response->error = KM_ERROR_INVALID_OPERATION_HANDLE;
@@ -259,6 +262,9 @@
 
 void GoogleKeymaster::FinishOperation(const FinishOperationRequest& request,
                                       FinishOperationResponse* response) {
+    if (response == NULL)
+        return;
+
     OpTableEntry* entry = FindOperation(request.op_handle);
     if (entry == NULL) {
         response->error = KM_ERROR_INVALID_OPERATION_HANDLE;