Registry: Guard against Object prototype keys in lookup()

See also a422b0b which fixed this previously for EventEmitter.

hasOwnProperty makes .lookup('constructor') and other inherited
prototype keys work correctly.

Using lookup everywhere makes it possible to override it usefully.

Change-Id: Ieda909509fdafcacc5fe7b795737106716f4ec42
Merge "Registry: Guard against Object prototype keys in lookup()"