Tree is closed for linux CI upgrade

[Josh Bowman-Matthews]

Since I have successfully performed builds on Xenial-based linux
machines, I am closing the tree so I can upgrade the servo-linux[1-6]
and servo-linux-cross[1-3] build machines from Trusty to Xenial. I hope
to have the process complete by end of day. I'll track my progress in
https://github.com/servo/saltfs/pull/957, and you can see the Servo-side
changes which will be the first PR to merge in the new setup at
https://github.com/servo/servo/pull/23182.

Cheers,
Josh

[Josh Bowman-Matthews]

Everything worked smoothly the first time and
https://github.com/servo/servo/pull/23182 successfully merged! I have
reopened the tree, and I'll deal with the remaining TravisCI issues in
https://github.com/servo/saltfs/pull/957 separately. If you need to
deploy any changes to saltfs, please check with me first.

Cheers,
Josh

[Josh Bowman-Matthews]

After finally figuring out how to resolve the TravisCI failures, and
unexpectedly having to upgrade servo-master1 to xenial today, we are
back to a status quo of deploying salt-based changes off of the saltfs
master branch. Sorry that it took so long!