Noticed when using an MUS with a Merlin-DV engine. When the decoupler was staged from below the engine, the fairing was reparented and stayed attached to the -engine- and not the decoupler.

When the vessel was reloaded, this errantly-placed-fairing was gone. The issue appears to be in the detection of which part the fairing should be re-parented to when jettisoned. A brief look over the code does not show anything to be immediately amiss. Will need to add some additional debug logging and find out how/where the parent detection is returning incorrect values.

Duplicate of #800