Maybe you need to add it to the dhclient configuration file: send host-name "journeyhawk"; Yes, yet another location where that information is kept and must be changed when you change your hostname. Is there a decent solution to this problem yet?
You should be able to evaluate hostname, like one of the following: send host-name "$(eval hostname)"; send host-name "`hostname`"; or something like that... mostly depending on your shell support. Enjoy :)