update_engine: fixed warnings from cpplint

Fixed all the cpplint warnings in update engine.

BUG=None
TEST=Unit tests still pass.

Change-Id: I285ae858eec8abe0b26ff203b99a42a200ceb71c
Reviewed-on: https://chromium-review.googlesource.com/204027
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/http_common.cc b/http_common.cc
index c230620..a3bd7f8 100644
--- a/http_common.cc
+++ b/http_common.cc
@@ -71,4 +71,4 @@
   return (is_found ? http_content_type_table[i].str : NULL);
 }
 
-} //  namespace chromeos_update_engine
+}  // namespace chromeos_update_engine