/usr/lib/x86_64-linux-gnu/unity8/qml/Unity/Notifications/libnotifyclientplugin.so is in qtdeclarative5-unity-notifications-plugin 0.1.3+15.10.20151021-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/unity8/qml/Unity/Notifications/libnotifyclientplugin.so.1