Bug 1382972 - disable wpt test RTCPeerConnection-addIceCandidate.html r=ng

This test (plus a couple others) were imported from upstream before they
were fully baked.

MozReview-Commit-ID: GDiFsZ8g229

--HG--
extra : rebase_source : 90e514fe100f7de89da0d34afe96262b6880838e

testing/web-platform/meta/webrtc/RTCPeerConnection-addIceCandidate.html.ini

@@ -30,3 +30,5 @@
   [Add candidate with sdpMid belonging to different ufrag should reject with OperationError]
     expected: FAIL
 
+  [Add valid candidate should never resolve when pc is closed]
+    disabled: https://bugzilla.mozilla.org/show_bug.cgi?id=1382972