s4-common: update wifi init

bt-pan: dhcpcd: Allow address claim by ARP, don't set gateway
p2p: dhcpcd: -a performs no function (see if-options.c in dhcpcd source)
wlan0: dhcpcd: set domainname as given by DHCP server, set gateway

wpa/p2p_supplicant: set disable_scan_offload=1

Change-Id: I23f23b310357e13fcbde017de8a016618a6b8514