Stop sched_scan in number of cases where it should not be running

Stop sched_scan in number of cases where it should not be running

When a P2P group is removed, we better not leave possibly started
sched_scan running. This could happen when a separate group interface
was not used.

In addition, it looks safer to explicitly stop sched_scan before
starting P2P Listen or Find operations to make sure the offloaded
scanning is not running when doing similar P2P operations.

Signed-hostap: Jouni Malinen <jouni@qca.qualcomm.com>