Re-evalutes the ICE role on ICE restart.
Also unifies the logic of ICE restart.

BUG=1775
R=juberti@google.com, juberti@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/20619004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6510 4adac7df-926f-26a2-2b94-8c16560cd09d