Marionette uses nsIServerSocket which only allows to create a IPv4 listener.
On systems where IPv6 has precedence Marionette client will automatically
use the IPv6 address for `localhost` and will fail to connect to Marionette.
As such we should make sure that Marionette client connects to "127.0.0.1"
by default.
MozReview-Commit-ID: Fwzfa6CwBhX
--HG--
extra : rebase_source : c9f3f80074a18bd94b0836e648da4934e5ffa877
Adds instructions in how to use Taskcluster and interactive
tasks (one click loaners) to debug failing tests.
MozReview-Commit-ID: 5fImVtYUxfY
--HG--
extra : rebase_source : 5fd52f7842a6fea969dd1bf3d8a024bf87a5d62f