In situations where the driver does background scanning and sends a
steady stream of scan results, wpa_supplicant would continually
reschedule the scan. This resulted in specific SSID scans never
happening for a hidden AP, and the supplicant never connecting to the AP
because it never got found. Instead, if there's an already scheduled
scan, and a request comes in to reschedule it, and there are enabled
scan_ssid=1 network blocks, let the scan happen anyway so the hidden
SSID has a chance to be found.
