improve detection of hotspot mode

hotspot mode is not well represented with the WifiState stuff.  It can be
active when the WifiState is DISABLED or UNKNOWN.  Also, when switching
from active wifi to hotspot mode, WIFI_STATE_DISABLING broadcasts will be
sent, but WIFI_STATE_DISABLED/WIFI_STATE_UNKNOWN will not.

F-Droid/src/org/fdroid/fdroid/net/WifiStateChangeService.java

@@ -46,6 +46,8 @@ public class WifiStateChangeService extends Service {
                NetworkInfo is only passed via WifiStateChangeReceiver */
             Log.i(TAG, "ni == " + ni + "  wifiState == " + printWifiState(wifiState));
             if (wifiState == WifiManager.WIFI_STATE_ENABLED
+                    || wifiState == WifiManager.WIFI_STATE_DISABLING   // might be switching to hotspot
+                    || wifiState == WifiManager.WIFI_STATE_DISABLED   // might be hotspot
                     || wifiState == WifiManager.WIFI_STATE_UNKNOWN) { // might be hotspot
                 if (asyncTask != null) {
                     asyncTask.cancel(true);
@@ -73,9 +75,15 @@ public class WifiStateChangeService extends Service {
                     if (wifiState == WifiManager.WIFI_STATE_ENABLED) {
                         wifiInfo = wifiManager.getConnectionInfo();
                         FDroidApp.ipAddressString = formatIpAddress(wifiInfo.getIpAddress());
-                    } else
+                    } else if (wifiState == WifiManager.WIFI_STATE_DISABLED
+                            || wifiState == WifiManager.WIFI_STATE_DISABLING) {
+                        // try once to see if its a hotspot
                         FDroidApp.ipAddressString = getIpAddressFromNetworkInterface();
-                    // TODO turning off a hotspot leaves wifiState as UNKNOWN with no IP, and this goes until next wifi change
+                        if (FDroidApp.ipAddressString == null)
+                            return null;
+                    } else {  // a hotspot can be active during WIFI_STATE_UNKNOWN
+                        FDroidApp.ipAddressString = getIpAddressFromNetworkInterface();
+                    }
                     Thread.sleep(1000);
                     if (BuildConfig.DEBUG) {
                         Log.d(TAG, "waiting for an IP address...");