Add timeout for localIP

[pennam]

Adds timeout for localIP() instead of waiting a fixed amount of time. Other proposed solution #408

Fixes #406

[JAndrassy]

WiFi.begin is blocking until DHCP gets an IP address. there is no reason to have a timeout in localIP(). it will only return immediately if WiFi.begin was successful or wait the complete timeout if WiFi.begin didn't run or didn't connect.
there is nothing to wait for.

[pennam]

@JAndrassy I get your point. I do not understand why in the original code localIP() was doing the retry loop so I opted for a less impacting change. Probably @maidnl has some hints about the original reason of the retries.

[maidnl]

@pennam if I remember correctly the problem was related to the use of begin() and, immediately after, localIP(). In this case the ESP32 took some (little) time to set up the address and give it back so that the first call could fail and give the impression of a failed connection or wrong DHCP set up. For this reason I added this "retry" mechanism. I think is safe to keep some sort of retry.