flush: factor out the pre-loading of interfaces
flush: factor out the pre-loading of interfaces

Move the pre-loading of interfaces and address assignments to a separate
function. Machine plenaries need the management interfaces only. There's
no need to sort the interfaces by name, the plenary generators do that
already.

Change-Id: I7b655d9e918681b766ed6ceb6060e10b3b711532
Reviewed-by: Zoltan Sebestyen <be2314d0afde2d2352aeb623a228e572c9b6cb8b@morganstanley.com>

quattor/aquilon,quattor/aquilon,guillaume-philippon/aquilon,guillaume-philippon/aquilon,quattor/aquilon,guillaume-philippon/aquilon