shill: Add C++11 override specifier to destructors of derived classes.

BUG=None
TEST=`USE=wimax FEATURES=test emerge-$BOARD platform2`

Change-Id: I88d4e29165869b26924cccb94ac940dc8961c312
Reviewed-on: https://chromium-review.googlesource.com/212267
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
diff --git a/mock_supplicant_bss_proxy.h b/mock_supplicant_bss_proxy.h
index 36de1e4..825969a 100644
--- a/mock_supplicant_bss_proxy.h
+++ b/mock_supplicant_bss_proxy.h
@@ -15,7 +15,7 @@
 class MockSupplicantBSSProxy : public SupplicantBSSProxyInterface {
  public:
   MockSupplicantBSSProxy();
-  virtual ~MockSupplicantBSSProxy();
+  ~MockSupplicantBSSProxy() override;
 
   MOCK_METHOD0(Die, void());  // So we can EXPECT the dtor.