Disable scaling of the cfs tunables.

The cfs tunables auto-scale with the number of active cpus by default. Given
that the tunable settings are in device-independent code and it's not
known how many cores are currently active when the init.rc file runs,
the cfs tunables can vary pretty significantly across devices depending
on the state at boot. Disable scaling of the the tunables so that we
can get more consistent behavior of cfs across devices. If we want to
do per-device tuning of these values, we can override what's written
here in device specific files.

Bug: 22634118
Change-Id: Id19b24ef819fef762521e75af55e6d4378cfc949