[test] Restrict msan to default variant.
[test] Restrict msan to default variant.

NOTRY=true
BUG=chromium:425187
LOG=n
TBR=Sven Panne, titzer

Review URL: https://codereview.chromium.org/1110923002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#28097}

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh