Code review comment for lp:~julian-edwards/maas/enlist-nodegroup-bug-1274926

As discussed this morning, this change means earlier versions of maas-enlist will fail to register nodes (because the API call will not contain the 'autodetect_nodegroup' parameter). This means we won't be able to enlist/commission nodes using pre-Trusty series. In conjunction with bug 1279310, this restricts the number of series that can be used for enlistment down to zero :). (Note that we have a manual workaround (see the bug description)).