ensure result adjacencies start empty
ensure result adjacencies start empty

Any existing list would be mutated by result(), which is bad.

Note that all the existing newJoinResults() call sites pass in nodes
with no adjacencies, so this is purely a safety measure.

kinvolk/scope,alban/scope,kinvolk/scope,weaveworks/scope,kinvolk/scope,kinvolk/scope,alban/scope,weaveworks/scope,weaveworks/scope,kinvolk/scope,weaveworks/scope,alban/scope,alban/scope,kinvolk/scope,weaveworks/scope,weaveworks/scope,alban/scope,alban/scope