sched/numa: Reset scan rate whenever task moves across nodes

Currently task scan rate is reset when numa balancer migrates the task
to a different node. If numa balancer initiates a swap, reset is only
applicable to the task that initiates the swap. Similarly no scan rate
reset is done if the task is migrated across nodes by traditional load
balancer.

Instead move the scan reset to the migrate_task_rq. This ensures the
task moved out of its preferred node, either gets back to its preferred
node quickly or finds a new preferred node. Doing so, would be fair to
all tasks migrating across nodes.

specjbb2005 / bops/JVM / higher bops are better
on 2 Socket/2 Node Intel
JVMS  Prev    Current  %Change
4     210118  208862   -0.597759
1     313171  307007   -1.96825

on 2 Socket/4 Node Power8 (PowerNV)
JVMS  Prev     Current  %Change
8     91027.5  89911.4  -1.22611
1     216460   216176   -0.131202

on 2 Socket/2 Node Power9 (PowerNV)
JVMS  Prev    Current  %Change
4     191918  196078   2.16759
1     207043  214664   3.68088

on 4 Socket/4 Node Power7
JVMS  Prev     Current  %Change
8     58462.1  60719.2  3.86079
1     108334   112615   3.95167

dbench / transactions / higher numbers are better
on 2 Socket/2 Node Intel
count  Min      Max      Avg      Variance  %Change
5      11851.8  11937.3  11890.9  33.5169
5      12511.7  12559.4  12539.5  15.5883   5.45459

on 2 Socket/4 Node Power8 (PowerNV)
count  Min      Max      Avg      Variance  %Change
5      4791     5016.08  4962.55  85.9625
5      4709.28  4979.28  4919.32  105.126   -0.871125

on 2 Socket/2 Node Power9 (PowerNV)
count  Min      Max      Avg     Variance  %Change
5      9353.43  9380.49  9369.6  9.04361
5      9388.38  9406.29  9395.1  5.98959   0.272157

on 4 Socket/4 Node Power7
count  Min      Max      Avg      Variance  %Change
5      149.518  215.412  179.083  21.5903
5      157.71   184.929  174.754  10.7275   -2.41731

Cc: Rik van Riel <riel@surriel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1533276841-16341-6-git-send-email-srikar@linux.vnet.ibm.com