sched/fair: Check env src_grp_nr_running for active load balance

When do active load balance needed check, the environment
may changed, so check for env's src_grp_nr_running before
src rq h_nr_running check to ensure that's the same
envrionment data we tried to do active load balance.

Change-Id: Ia9539a43e9769c4936f06ecfcc11864984c50c29
Signed-off-by: Maria Yu <aiquny@codeaurora.org>