Refactored to make MDnsSocketFactory return array of sockets.
MDnsClinet will just listen and send packet to those sockets without knowing address family or interface.

BUG=297690
TBR=thestig, for c/tools/

Review URL: https://codereview.chromium.org/87693002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238042 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238042