Comment 2 for bug 1269664

Expectations are for MAAS to find an unused slot and not expect to overwrite an existing user in a particular slot.

Use case:

in a DC, I have 11 admins who have CIMC access to my UCS servers, each has an account on the CIMC.
Then I move the server into MAAS and instead of maas finding slot 12, it overwrites slot 10, and Bill the Admin can no longer log into the CIMC because his account has been overwritten.

What I did was change slot 10 to a user, joebob, with his own password and then re-enlisted the machine... at this time there were only two accounts in the ... 15 available slots on the CIMC, Admin and Joebob. But rather than use an open slot, MAAS overwrote slot 10.

Ultimately, perhaps something like this:
MAAS looks for an open slot, and if it doesn't find one, enlistment fails (or succeeds with caveats) and the UI displays a message like: Server xyz.local enlisted but there is no maas user in the management system. Please correct this and re-enlist server xyz.local or edit the server with valid admin username and password before proceeding to Commissioning stage."

When I add a machine manually, I can enter an admin username and password for the BMC/AMT device, so there's really no reason maas can't keep that data and use it instead of creating a second admin user with it's own password. At least that's my naive view of it.