physics::Link::Fini() leaves zombie update functions in sdf

[osrf-migration]

Original report (archived issue) by Yoshito Okada (Bitbucket: yoshito-okada).

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Some member functions of physics::Link set update functions for the link’s sdf (ex. https://github.com/osrf/gazebo/blob/63cce1db38286ba373cfb5e54c2a58dfb4d42501/gazebo/physics/Link.cc#L159 ). And these update functions remains after the link has been removed by physics::Model::RemoveChild() or others. If these zombie update functions are called by Update() of a parent model’s sdf or others, a runtime error or segmentation fault occur.

In my opinion, physics::Link::Fini() should make the final call of Update() to write link’s final states to the sdf, and then detach update functions from the sdf.

Finally, this is an issue not only for physics::Link, but also for all classes which set update functions (as of now, Battery, Inertial, Link and Model).