Remove DHCP-block from interface "client"

For parker we need DHCP on the client interface. Ths rule
prevents us from doing so.
In addition: make sure old rules will be deleted on upgrade.

package/gluon-client-bridge/luasrc/lib/gluon/upgrade/300-gluon-client-bridge-network

@@ -46,5 +46,7 @@ uci:section('dhcp', 'dhcp', 'local_client', {
 	ignore = true,
 })
 
+uci:delete('dhcp', 'local_client')
+
 uci:save('dhcp')
 uci:save('firewall')