sched/fair: update_rq_clock after nr_running check in load balance path

As there is a possibility that number of running tasks could be
less than or equal to one and the check for nr_running leads to
not to move of the tasks, updating update_rq_clock before check
is wrong, fix it by moving update_rq_clock after the check.

Change-Id: I1719a5482af3c35131e18e9fd521cb9e5d2de2ae
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>