We must not throw when seeing a cycle while trying to resolve a name through
star exports.  (It may be surprising that we do have to throw when seeing an
ambiguity, but this is what the spec says.)

R=adamk@chromium.org
BUG=v8:1569

Review-Url: https://codereview.chromium.org/2376563002
Cr-Commit-Position: refs/heads/master@{#39787}