health: do not use default destructor.

Otherwise, clients will need to know how to destroy
LinkedCallback, a hidden class.

Test: builds
Bug: 177269435
Change-Id: I89532755da16b672c4cbece55b943306f68cdb9e

health/aidl/default/Health.cpp

@@ -60,6 +60,8 @@ Health::Health(std::string_view instance_name, std::unique_ptr<struct healthd_co
     battery_monitor_.init(healthd_config_.get());
 }
 
+Health::~Health() {}
+
 //
 // Getters.
 //

health/aidl/default/include/health-impl/Health.h

@@ -43,6 +43,7 @@ class Health : public BnHealth, public HalHealthLoopCallback {
     // A subclass may modify |config| before passing it to the parent constructor.
     // See implementation of Health for code samples.
     Health(std::string_view instance_name, std::unique_ptr<struct healthd_config>&& config);
+    virtual ~Health();
 
     ndk::ScopedAStatus registerCallback(
             const std::shared_ptr<IHealthInfoCallback>& callback) override;