Increase WiFi.begin() default timeout to 15s (#1041)

Fixes #1031, or at least covers the case of slower associations.

Author: earlephilhower

libraries/WiFi/src/WiFiClass.h

@@ -381,7 +381,7 @@ class WiFiClass {
     void feedWatchdog();
 
 private:
-    int _timeout = 10000;
+    int _timeout = 15000;
     String _ssid;
     String _password;
     bool _wifiHWInitted = false;