DNS list is reversed priority.

Manifest
-------------
networks:
  - name: default
    type: manual
    cloud_properties:
      security_groups:
        xxxxxxx
      availability_zone: ap-northeast-1a
    dns:
      - 10.0.1.10
      - 10.0.0.2
    ...
-

Expected resolv.confd
-------
nameserver 10.0.1.10
nameserver 10.0.0.2

-
Actual resolv.conf
----------
nameserver 10.0.0.2
nameserver 10.0.1.10
nameserver 10.0.0.2
(10.0.0.2 is DHCP DNS )
-

Change-Id: I53de2ca11bd23d3d5561112180aff2da6fbae006
Merge "DNS list is reversed priority."