[Patches from Fedora package] Network booting changes

[Lubomir Rintel]

Hi,

chained to this message are fixes and enhancements from Fedora package (Red Hat 
Enterprise Linux ships them too) related to network booting. I've made only 
minor changes to them, described in individual commit messages.

Please have a look, and eventually merge; I think all of them are pretty 
straightforward.

Thanks in advance for feedback!
Lubo