setup-interfaces: find essids when SSID List capability present

When a essid has the 'SSID List' extended capibility, the find_essids function will not return that ssid. That's because the $1 ~ /SSID/ awk pattern will match that line. The ssid variable then is set to an empty value because there is no : (field separate) in that line, so $2 is empty.

The terminator of the statemachine then skips this essid, because it checks if the ssid variable is not empty.

We can fix this by making sure the field ends with SSID, which is not the case with the SSID List line.

Partial output of iw dev wlan0 scan:

        Extended capabilities:
                 * Extended Channel Switching
                 * TFS
                 * WNM-Sleep Mode
                 * TIM Broadcast
                 * BSS Transition
                 * SSID List
                 * Operating Mode Notification
                 * 6
                 * Max Number Of MSDUs In A-MSDU is unlimited

Reported-by: invoked