cpuset: Restore tasks affinity while moving across cpusets

When tasks move across cpusets, the current affinity settings
are lost. Cache the task affinity and restore it during cpuset
migration. The restoring happens only when the cached affinity
is subset of the current cpuset settings.

Change-Id: I6c2ec1d5e3d994e176926d94b9e0cc92418020cc
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
[satyap@codeaurora.org: fix trivial merge conflicts and
replace cs->cpus_requested with cs->cpus_allowed]
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>