Don't set drafts to be loaded initially.

This was preventing discarding from working properly. The draft appeared
loaded, but had no ID, so it was never fetched and therefore never
destroyed.
Fix unit tests with gCommentIssueManager.

gCommentIssueManager was being referenced when creating the comment
dialog, but in a way that wouldn't allow undefined if it didn't exist.
This impacted unit tests. Now, a commentIssueManager can either be set
in options, or window.gCommentIssueManager will be referenced.