Do not retry privet requests on URL fetcher errors

Do not retry privet requests when the request errors out due to a reset
connection or the like.

BUG=334497

Review URL: https://codereview.chromium.org/140783012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245749 0039d316-1c4b-4281-b951-d872f2087c98
Privet notifications should check for _privet instead of _privet._tcp.local.
DNS packet may contain no full string.

BUG=335822

Review URL: https://codereview.chromium.org/140983008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245750 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245750