Fix `bin/repository importing` for CLOSEABLE flag

Summary: After adding the CLOSEABLE flag, `bin/repository importing` reports CLOSEABLE commits with no information. Just don't report these, for consistency with the old behavior. Adding flags to show them might be nice at some point if we run into issues where that output would be useful.

Test Plan: Ran `bin/repositroy importing` on a repository with CLOSEABLE commits.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D8024