NetworkManager: do not tend missing hardware

[John Reiser]

When booting a Live spin, how can I tell NetworkManager to avoid any hardware
that is not present?  There is [and will be] no ISDN, no ADSL, no dialup modem,
no Bluetooth, no wired ethernet; and I want to reduce RAM usage as much as possible.
This is to support netbooks and other machines with only 1GB RAM.
Already I found setroubleshootd sitting on 55MB of physical RAM (rhbz #953676),
but I want more.

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