concern - `UserDelete` method called on only existing BMC user

[jacobweinstock]

With this interface method below, we could potentially lock ourselves out of a BMC by removing all users. If the user given is the only user in the BMC, we might not want to delete it.

bmclib/bmc/user.go

Line 23 in 85f37d5

UserDelete(ctx context.Context, user string) (ok bool, err error)

We should probably add some comments to the method so that implementors know they should check if the user is the only user left before deleting. We could also maybe add a parameter like force bool to delete the user regardless.