[RESEND PATCH] sched: consider missed ticks when updating global cpu load

[byungchul.park]

From: Byungchul Park <byungchul.park@xxxxxxx>

hello,

i have already sent this patch about 1 month ago.
(see https://lkml.org/lkml/2015/8/13/160)

now, i am resending the same patch with adding some additional commit 
message.

thank you,
byungchul

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