Use super to get much-needed MRO magic in constructor. (#1158968)

super does some magic along the lines of running superclass constructors
breadth-first, which is necessary for container devices that inherit first
from a non-container class.

(cherry picked from commit 274e91e1966cbe74f64743e028d8088f712c8ae0)
Device status can never be True for non-existent devices. (#1156058)

(cherry picked from commit e7b45e635b8850de55c4e20085f1bd5dae8b4341)