rtc_unittest: copied gtest excludes from libjingle_p2p_unittest since its tests have move to rtc_unittests.

BUG=3925
R=marpan@google.com

Review URL: https://webrtc-codereview.appspot.com/28739004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7466 4adac7df-926f-26a2-2b94-8c16560cd09d