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/file_descriptor.h b/file_descriptor.h
index 8a31180..391a650 100644
--- a/file_descriptor.h
+++ b/file_descriptor.h
@@ -82,7 +82,7 @@
 class EintrSafeFileDescriptor : public FileDescriptor {
  public:
   EintrSafeFileDescriptor() : fd_(-1) {}
-  virtual ~EintrSafeFileDescriptor() {};
+  virtual ~EintrSafeFileDescriptor() {}
 
   // Interface methods.
   virtual bool Open(const char* path, int flags, mode_t mode);