Restart AccountPushControllers when connectivity returns

PushController.onConnectivityChanged() is not only called when the active network changes, but also when connectivity returns (offline -> online). In that case we need to restart the AccountPushControllers.

app/core/src/main/java/com/fsck/k9/controller/push/PushController.kt

@@ -105,6 +105,8 @@ class PushController internal constructor(
                     accountPushController.reconnect()
                 }
             }
+
+            updatePushers()
         }
     }