Fix plugin crashes caused by failing assertions

The Maps plugin creates some helper CordovaPlugin objects and registers
them with PluginManager, and, at the same time, calls
'privateInitialize' manually. This causes an assertion to trip inside
Cordova Android.

The failing assertion only affects debug-mode builds that use a new
Android SDK. See also
mapsplugin#2900

src/android/plugin/google/maps/CordovaGoogleMaps.java

@@ -454,6 +454,7 @@ public void getMap(final JSONArray args, final CallbackContext callbackContext)
     pluginMap.mapCtrl = CordovaGoogleMaps.this;
     pluginMap.self = pluginMap;
 
+    pluginMap.cordova = null; // avoid failure caused by repreated initialization
     PluginEntry pluginEntry = new PluginEntry(mapId, pluginMap);
     pluginManager.addService(pluginEntry);
 
@@ -475,6 +476,7 @@ public void getPanorama(final JSONArray args, final CallbackContext callbackCont
     pluginStreetView.mapCtrl = CordovaGoogleMaps.this;
     pluginStreetView.self = pluginStreetView;
 
+    pluginStreetView.cordova = null; // avoid failure caused by repreated initialization
     PluginEntry pluginEntry = new PluginEntry(mapId, pluginStreetView);
     pluginManager.addService(pluginEntry);
 

src/android/plugin/google/maps/PluginMap.java

@@ -613,6 +613,7 @@ public synchronized void loadPlugin(final JSONArray args, final CallbackContext
       plugins.put(pluginName, pluginEntry);
       mapCtrl.pluginManager.addService(pluginEntry);
 
+      plugin.cordova = null; // avoid failure caused by repreated initialization
       plugin.privateInitialize(pluginName, cordova, webView, null);
 
       plugin.initialize(cordova, webView);
@@ -666,6 +667,7 @@ public void create(final JSONArray args, final CallbackContext callbackContext)
       pluginMap = PluginMap.this;
       pluginMap.mapCtrl.pluginManager.addService(pluginEntry);
 
+      plugin.cordova = null; // avoid failure caused by repreated initialization
       plugin.privateInitialize(className, cordova, webView, null);
       plugin.initialize(cordova, webView);
       ((MyPluginInterface)plugin).setPluginMap(PluginMap.this);