harness: Take ownership of floating references (pads, elements) passed to the harness

Without this bindings get confused about the meaning of references, and
we really own these references if they are not already owned by
something else.
3 jobs for harness-floating-references in 7 minutes and 22 seconds (queued for 27 minutes and 34 seconds)
Status Job ID Name Coverage
  Preparation
passed #50625
manifest

00:00:30

 
  Build
passed #50626
build fedora x86_64

00:03:46

 
  Full Builds
passed #50627
build android arm64 api28

00:03:05