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/update_manager/fake_state.h b/update_manager/fake_state.h
index eaaf68e..f47aa78 100644
--- a/update_manager/fake_state.h
+++ b/update_manager/fake_state.h
@@ -33,7 +33,7 @@
 
   virtual ~FakeState() {}
 
-  // Downcasted detters to access the fake instances during testing.
+  // Downcasted getters to access the fake instances during testing.
   virtual FakeConfigProvider* config_provider() override {
     return &config_provider_;
   }