[ACS41][Patch Request] CLOUDSTACK-1461: Don't set dns server for non-default ipv6 network

[Sheng Yang]

Already checked in master.

commit e35ce6587a2519fdbc56e8859ad6aa7dac00dd47
Author: Sheng Yang <sheng.y...@citrix.com>
Date:   Fri Mar 8 17:42:06 2013 -0800

    CLOUDSTACK-1461: Don't set dns server for non-default ipv6 network

    The non-default parameter can be used by ipv4 as well in the future.

Thanks!

--Sheng