sched: consider runnable load average in move_tasks

Except using runnable load average in background, move_tasks is also
the key functions in load balance. We need consider the runnable load
average in it in order to the apple to apple load comparison.

Morten catch a div u64 bug on ARM, thanks!

Signed-off-by: Alex Shi <alex.shi@intel.com>
sched: remove blocked_load_avg in tg

blocked_load_avg sometime is too heavy and far bigger than runnable load
avg, that make balance make wrong decision. So remove it.

Changlong tested this patch, found ltp cgroup stress testing get better
performance: https://lkml.org/lkml/2013/5/23/65
---
3.10-rc1          patch1-7         patch1-8
duration=764   duration=754   duration=750
duration=764   duration=754   duration=751
duration=763   duration=755   duration=751

duration means the seconds of testing cost.
---

And Jason also tested this patchset on his 8 sockets machine:
https://lkml.org/lkml/2013/5/29/673
---
When using a 3.10-rc2 tip kernel with patches 1-8, there was about a 40%
improvement in performance of the workload compared to when using the
vanilla 3.10-rc2 tip kernel with no patches. When using a 3.10-rc2 tip
kernel with just patches 1-7, the performance improvement of the
workload over the vanilla 3.10-rc2 tip kernel was about 25%.
---

Signed-off-by: Alex Shi <alex.shi@intel.com>
Tested-by: Changlong Xie <changlongx.xie@intel.com>
Tested-by: Jason Low <jason.low2@hp.com>