If DNS address received in IPv6 subnet is unspecified, don't convert it to IPv6 address structure.
Closes-Bug: #1401866

Change-Id: If0ecf64adccaf10860af2b248caf7111ef4ef9c8
Merge "If DNS address received in IPv6 subnet is unspecified, don't convert it to IPv6 address structure. Closes-Bug: #1401866"