Make the example action script less likely to result in failures

Use "=" instead of "==" and add an example statement between "then"
and "fi".

wpa_supplicant/README

@@ -865,13 +865,14 @@ script:
 IFNAME=$1
 CMD=$2
 
-if [ "$CMD" == "CONNECTED" ]; then
+if [ "$CMD" = "CONNECTED" ]; then
     SSID=`wpa_cli -i$IFNAME status | grep ^ssid= | cut -f2- -d=`
     # configure network, signal DHCP client, etc.
 fi
 
-if [ "$CMD" == "DISCONNECTED" ]; then
+if [ "$CMD" = "DISCONNECTED" ]; then
     # remove network configuration, if needed
+    SSID=
 fi