WifiConfiguration: show more detail in toString()

When debugging WiFi issues, it's helpful to know whether
or not a network uses a hidden SSID. Update
WifiConfiguration.toString(), to provide this information.

BUG=26836097
TEST=capture bugreport, verify "HIDDEN: false" is present for normal net
TEST=capture bugreport, verify "HIDDEN: true" is present for hidden net

Change-Id: I1f7c587fc2eda358e0868e9a7ef0bb2058e726a8

wifi/java/android/net/wifi/WifiConfiguration.java

@@ -1356,6 +1356,7 @@ public class WifiConfiguration implements Parcelable {
                 append(" PROVIDER-NAME: ").append(this.providerFriendlyName).
                 append(" BSSID: ").append(this.BSSID).append(" FQDN: ").append(this.FQDN)
                 .append(" PRIO: ").append(this.priority)
+                .append(" HIDDEN: ").append(this.hiddenSSID)
                 .append('\n');