stop lwIP dhcp client when WiFi goes off. (#5703)
stop lwIP dhcp client when WiFi goes off. (#5703)

* stop lwIP dhcp client with WiFi goes off.

* stop dhcp-client when really unused

esp8266/Arduino,sticilface/Arduino,sticilface/Arduino,Lan-Hekary/Arduino,sticilface/Arduino,sticilface/Arduino,esp8266/Arduino,esp8266/Arduino,Lan-Hekary/Arduino,Lan-Hekary/Arduino,esp8266/Arduino,esp8266/Arduino,Lan-Hekary/Arduino,Lan-Hekary/Arduino,sticilface/Arduino