test: clarify dropMembership() call
According to docs, dropMembership() is automatically called by the kernel when the socket is closed, and most apps will never need to call it. We don't need it so let's keep the code simpler.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
According to docs, dropMembership() is automatically called by the kernel when the socket is closed, and most apps will never need to call it. We don't need it so let's keep the code simpler.