Only create wifi networks file if necessary

src/freedombone-utils-wifi

     ifconfig ${WIFI_INTERFACE} up
 }
 
+function wifi_networks_file_header {
+    echo $'# Add wifi networks as follows:' > $WIFI_NETWORKS_FILE
+    echo '#' >> $WIFI_NETWORKS_FILE
+    echo $'# MySSID' >> $WIFI_NETWORKS_FILE
+    echo $'# wpa2-psk' >> $WIFI_NETWORKS_FILE
+    echo $'# myWifiPassphrase' >> $WIFI_NETWORKS_FILE
+    echo '#' >> $WIFI_NETWORKS_FILE
+    echo $'# AnotherSSID' >> $WIFI_NETWORKS_FILE
+    echo $'# none' >> $WIFI_NETWORKS_FILE
+    echo '#' >> $WIFI_NETWORKS_FILE
+}
+
 function create_networks_interactive {
     remove_config_param "WIFI_INTERFACE"
     update_wifi_adaptors
         rm $WIFI_NETWORKS_FILE
     fi
 
-    echo $'# Add wifi networks as follows:' > $WIFI_NETWORKS_FILE
-    echo '#' >> $WIFI_NETWORKS_FILE
-    echo $'# MySSID' >> $WIFI_NETWORKS_FILE
-    echo $'# wpa2-psk' >> $WIFI_NETWORKS_FILE
-    echo $'# myWifiPassphrase' >> $WIFI_NETWORKS_FILE
-    echo '#' >> $WIFI_NETWORKS_FILE
-    echo $'# AnotherSSID' >> $WIFI_NETWORKS_FILE
-    echo $'# none' >> $WIFI_NETWORKS_FILE
-    echo '#' >> $WIFI_NETWORKS_FILE
-
     # By default connect to any open wifi
     WIFI_SSID=''
     WIFI_TYPE=$'open'
             continue
         fi
 
+        if [ ! -f $WIFI_NETWORKS_FILE ]; then
+            wifi_networks_file_header
+        fi
+
         # update the wifi networks file
         echo '' >> $WIFI_NETWORKS_FILE
         echo "$WIFI_SSID" >> $WIFI_NETWORKS_FILE