shill: Add "iSNSOptionData" ipconfig property

This property is used by iSNS clients to discover the location of iSNS
servers, according to RFC 4174.

BUG=chromium:570766
TEST=manual

Change-Id: Ibc4b8ee4e81a33923389ee3ff7e714f69e2161fb
Reviewed-on: https://chromium-review.googlesource.com/333667
Commit-Ready: Victor Dodon <printesoi@chromium.org>
Tested-by: Victor Dodon <printesoi@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
1 file changed