sched: qhmp_core: Fix possible hotplug race in set_cpus_allowed_ptr

Since a CPU may go offline after cpu_active_mask is used
to query active CPUs, set_cpus_allowed_ptr might inadverntently
pass an invalid cpu number to move_queued_task.

Fix this by ensuring that the cpumask op that uses cpu_active_mask
checks the return value.

CRs-Fixed: 1029014
Change-Id: Iab49c8140a00b8b644f5b4f6c87e2e298a8bb107
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>