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/constants.cc b/constants.cc
index eec9144..b68bd04 100644
--- a/constants.cc
+++ b/constants.cc
@@ -75,4 +75,4 @@
 const char kPrefsUrlSwitchCount[] = "url-switch-count";
 const char kPrefsWallClockWaitPeriod[] = "wall-clock-wait-period";
 
-}
+}  // namespace chromeos_update_engine