Keep running mdns client even if either IPv4 or IPv6 bind failed.

BUG=297212
NOTRY=true

Review URL: https://chromiumcodereview.appspot.com/23498056

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225155 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225155