buffet: Add flag to disable XMPP support

As a temporary work around to major source of flake in tests, allow
disabling XMPP support in tests.

BUG=brillo:769
TEST=FEATURES="test" USE="clang asan" emerge-gizmo buffet && \
     FEATURES="test" emerge-gizmo buffet

Change-Id: I41ca92bb77b77132c1a20c7018b0ce737b69cf60
Reviewed-on: https://chromium-review.googlesource.com/264392
Tested-by: Christopher Wiley <wiley@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Christopher Wiley <wiley@chromium.org>
6 files changed
tree: 543a40dc60b2ee578ccd945cf3db85179140aadc
  1. buffet/