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/extent_ranges_unittest.cc b/extent_ranges_unittest.cc
index ba00d0d..11b17ed 100644
--- a/extent_ranges_unittest.cc
+++ b/extent_ranges_unittest.cc
@@ -106,7 +106,7 @@
                                                            a_num)));
 }
 
-}  // namespace {}
+}  // namespace
 
 TEST(ExtentRangesTest, ExtentsOverlapTest) {
   ExpectRangesOverlapOrTouch(10, 20, 30, 10);