sched: fix a bug in handling top task table rollover

When frequency aggregation is enabled, there is a possibility of
rolling over the top task table multiple times in a single
window.

For example

- utra() is called with PUT_PREV_TASK for task 'A' which does not
belong to any related thread grp. Lets say window rollover happens.
rq counters and top task table rollover is done.

- utra() is called with PICK_NEXT_TASK/TASK_WAKE for task 'B' which
belongs to a related thread grp. Lets say this happens before
the grp's cpu_time->window_start is in sync with rq->window_start.
In this case, grp's cpu_time counters are rolled over and the
top task table is also rolled over again.

Roll over the top task table in the context of current running task
to fix this.

Change-Id: Iea3075e0ea460a9279a01ba42725890c46edd713
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>