Handle legacy scan interruption of sched_scan/PNO

Handle legacy scan interruption of sched_scan/PNO

While starting from PNO start context, the scheduled scan was not
setting the flag wpa_s->scanning. This was resulting in the subsequent
SCAN command to proceed further and send command to nl80211/cfg80211.
The expected behavior of cancelling sched_scan was not happening here.

While sched_scan is in progress and a legacy scan comes on the
cli/socket, the sched_scan is cancelled and normal scan is allowed to
continue. However, sometimes sched_scan cancelled event comes a bit
delayed and we will send out the scan command before the wpa_s->scanning
is cleared. Instead, reschedule the incoming scan req if the
wpa_s->scanning shows that it is still in progress.

Signed-hostap: Jithu Jance <jithu@broadcom.com>