Automatically setup dhcpv4 server just like it's done for dhcpv6.
To select whether odhcpd or dnsmasq are serving DHCPv4 requests there
still is the 'maindhcp' option. To make things less confusing, make
sure things really work out-of-the-box in case dnsmasq is not even
installed at the time the uci-defaults script is being run.
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
d79eeba688