Disable proxy device tests as they fail when run multi-threaded
Disable proxy device tests as they fail when run multi-threaded

See crbug.com/1151517 for details on the failure.
See b/173833661 for a longer term fix.

BUG=b:173833661
TEST=None

Change-Id: I82499b72e39ab524584807dcc35c3d0be7ab1bff
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2553215
Auto-Submit: Dennis Kempin <cd09796fb571bec2782819dbfd33307f65b1c778@google.com>
Reviewed-by: Derek Basehore <fb1ef5d447d8cd53e9e4511d7b18b7cdbb10397f@chromium.org>
Commit-Queue: Dennis Kempin <cd09796fb571bec2782819dbfd33307f65b1c778@google.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

google/crosvm,google/crosvm,google/crosvm,google/crosvm