[PrivacyPrivilegeManager] ResponseFetched Event was not fired about tizenfx

[xerrni]

@myroot
Please check my fix in #457 Pull Request

[myroot]

Not yet fixed

 static ResponseContext context = null;
 PrivacyPrivilegeManager.GetResponseContext("some privilege").TryGetTarget(out context);
 context.ResponseFetched += some_handler;
 context.ResponseFetched -= some_handler; // context was removed from s_responseMap
 PrivacyPrivilegeManager.GetResponseContext("some privilege"); // a new context was created and added in s_responseMap
 context.ResponseFetched += some_handler;  // It will not fired when Response was fetched

[xerrni]

@myroot
Please check current version.
I fixed issue mentioned in comment above.