MKRWAN 1310 only connects with 10s delay before join.OTTA

[guidosch]

Hi, my Arduino 1310 only connected to the TTN by adding a long delay between mode.begin and modem.joinOTTA. Without the delay I see several activation calls in the TTN console and finally a timeout with an error message that the module could not connect to LORA. May be this can be optimized in the library but I don't know how at the moment. May be the reason is, that there are many gateways round the place I live and the node tries to register at several of them.