update_engine: fixed remaining linter and some spelling errors

Fixed remaining errors from cpplint as well as some spelling errors
mostly in comments.

BUG=None
TEST=FEATURES=test emerge-link update_engine

Change-Id: I484988ab846ac5a3c68c016ddccfb247f225ec27
Reviewed-on: https://chromium-review.googlesource.com/208897
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/mock_http_fetcher.h b/mock_http_fetcher.h
index d5879f5..748acf1 100644
--- a/mock_http_fetcher.h
+++ b/mock_http_fetcher.h
@@ -97,7 +97,7 @@
   // already a timeout callback, and it should be deleted by the caller,
   // this will return false; otherwise true is returned.
   // If skip_delivery is true, no bytes will be delivered, but the callbacks
-  // still still be set if needed
+  // still be set if needed.
   bool SendData(bool skip_delivery);
 
   // Callback for when our glib main loop callback is called