vyatta-cfg-system: remove acpid and cpufrequtils from depends

Including the acpid and cpufrequtils packages in the XenSource image
causes a number of errors to be logged to the console on boot up, due
to either missing devices or access permissions on this platform.
Removing these packages from the dependencies list and adding them to a
chroot_local-packagelist instead allows them to be excluded in these
images, while still maintaining them in non XenSource images.
0.20.44+vyos2+lithium6