board/common: make dnsmasq authoritative, drop redundant options

Set dhcp-authoritative so clients with unexpired leases are not NAKed
after a router crash or factory reset that clears the lease database.

Drop the untagged suppress directives for options 3 (router) and 6
(dns-server): they conflict with the global options confd writes to
dnsmasq.d/, causing spurious "Ignoring duplicate dhcp-option" warnings.
Per-subnet tagged options already suppress auto-detection, and without
an active dhcp-range there is nothing to suppress anyway.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

board/common/rootfs/etc/dnsmasq.conf

@@ -2,6 +2,7 @@
 # managed by openresolv.  DHCP lease, VPN tunnel establishment,
 # and similar events feed servers and configuration to dnsmasq.
 domain-needed
+dhcp-authoritative
 
 # Allow configuration and cache clear over D-Bus
 enable-dbus
@@ -10,8 +11,6 @@ enable-dbus
 #dhcp-option=option:netmask
 #dhcp-option=28			# option:broadcast
 #dhcp-option=option:domain-name
-dhcp-option=option:router
-dhcp-option=option:dns-server
 dhcp-option=12			# option:hostname
 
 # Generated by openresolv