[testing] switch to use xenial for test from linux msan builder

Test from this builder consumes 6~7 machine hour in chrome pool per
hour averagely.
I took the stats from
http://shortn/_EstLqOoMvH

I fixed msan issue crbug.com/981731

Bug: 954450
Change-Id: I48a1ea540e8b46a79c44ca67afdbcfe122afa85a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1702267
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Auto-Submit: Takuto Ikuta <tikuta@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#679442}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: a1b47073daa98c72134cabb2a6dfec0b4b21f6ff
2 files changed