Bug 1607866 - disable netwerk/test/unit/test_trr.js for Thunderbird until bug 1608066 is resolved. r=valentin

Differential Revision: https://phabricator.services.mozilla.com/D59479

--HG--
extra : moz-landing-system : lando

netwerk/test/unit/xpcshell.ini

@@ -419,7 +419,8 @@ skip-if = os == "android"
 run-sequentially = node server exceptions dont replay well
 [test_trr.js]
 # http2-using tests require node available
-skip-if = os == "android"
+# test_trr.js is not working in Thunderbird due to bug 1608066.
+skip-if = os == "android" || appname == "thunderbird"
 [test_ioservice.js]
 [test_substituting_protocol_handler.js]
 [test_proxyconnect.js]