This just moves the perf-correctness leg to match the machine label of the rest
of our VS jobs.

Newer versions of git (I've seen this behavior on 2.13.1.windows.1 and
have not seen it on 2.11.1.windows.1) are much slower at writing out local
copies of refs after a fetch. Given that we fetch about 10K refs when
running each PR job this can lead to a massive slowdown in fetch times (on
the roslyn integration job, which has a newer version of git on the
workers compared to the other machines, we see fetch taking ~20 mins).

This changes all the Roslyn jobs to fetch just the PR they are going to
test, which speeds up the fetch significantly.

This reverts commit 2fba37a6.

This reverts commit 2fba37a6.

Looks like there is still fall out from the licensing issue.  VS integration tests still failing
at 100% due to a timeout issue.  Change them to not run by default while we look into this.

Can still be run manually for testing with

test vsintegration please

This means you can write a comment and then do the line by itself in
one GitHub comment. Otherwise it's requiring you have exactly one
per comment which is annoying.

Makes two changes to our groovy arguments

1. Prefer - over / which will let us remove our hacky argument change
legacy script.
1. Use the positive -testDesktop over -skipCoreClr verbs

The build depends on a global tool corflags to complete.  Unblocking build for now.

* add ubuntu 16.04 to CI

* added ubuntu.16.04 to the list of runtimes

* make ID unique

* switch perf correctness to dev15-rc

* Switch everything to latest-or-auto-dev15-rc

Further distinguish the integration tests name to 'windows_debug_vs-integration' and 'windows_release_vs-integration'