Fix 'enter' in autocomplete fields (djblets)
Handling of the 'enter' key for autocomplete fields like people and groups

wasn't correct, because the djblets handler (which submits the field) was

running before the autocomplete handler (which populates the field with the

current selected item).
The fix is to ensure that the keydown handlers run in the other order. This

change does the djblets side of that, adding a 'deferEventSetup' option.

Reproduced the bug. After this fix (and the matching reviewboard one), I can

press "enter" with a selected user and it will properly populate the field.