Disable stun for ippi account.

git-svn-id: http://csipsimple.googlecode.com/svn/trunk/CSipSimple@2370 9f815046-5998-e9c0-b7e2-ac03a23edfa4
Fixes issue 2666.

git-svn-id: http://csipsimple.googlecode.com/svn/trunk/CSipSimple@2371 9f815046-5998-e9c0-b7e2-ac03a23edfa4