init.rc: Remove cpu weight set on the root cgroup

It isn't allowed to change the cpu.share value for the root cgroup.
See kernel commit:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ec7dc8ac73e4a56ed03b673f026f08c0d547f597



This fixes the following error seen in dmesg:
init: write_file: Unable to write to '/dev/cpuctl/cpu.shares': Invalid argument

BUG: 28735908

Change-Id: I5ef359fb275792f99d13d35c62499026d354f6af
Signed-off-by: Irina Patru <irina.patru@intel.com>