[FS#214] Cannot configure different DNS for 2 interfaces

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - Vasiliy Solovey (miltador) 

Attached to Project - LEDE Project
Summary - Cannot configure different DNS for 2 interfaces
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - Medium
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - I want to set up different DNS servers for guest and lan interfaces.

My network configuration is here: [[https://github.com/miltador/lede-image-builder/blob/master/files/etc/config/network|https://github.com/miltador/lede-image-builder/blob/master/files/etc/config/network]]

With the above config I get all DNSs configured separately on each interface. 
In my case it is both Yandex DNS and OpenDNS on guest and lan. Instead of only OpenDNS on guest and only Yandex DNS on lan.

 - Device problem occurs on - TP-Link TL-WR842ND v1 
 - LEDE Trunk

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=214