Rename ActionExitCode to ErrorCode

Nowadays ActionExitCode is used throughout the codebase so use a more
generic name to reflect this.

BUG=chromium:216507
TEST=unit tests pass

Change-Id: I23d1d7e2676443251dbc42ed137fd018aadfa8a3
Reviewed-on: https://gerrit.chromium.org/gerrit/49512
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Commit-Queue: David Zeuthen <zeuthen@chromium.org>
Tested-by: David Zeuthen <zeuthen@chromium.org>
diff --git a/payload_state.h b/payload_state.h
index b12e6b0..1b0899c 100644
--- a/payload_state.h
+++ b/payload_state.h
@@ -38,7 +38,7 @@
   virtual void UpdateResumed();
   virtual void UpdateRestarted();
   virtual void UpdateSucceeded();
-  virtual void UpdateFailed(ActionExitCode error);
+  virtual void UpdateFailed(ErrorCode error);
   virtual bool ShouldBackoffDownload();
 
   virtual inline std::string GetResponseSignature() {