buffet: Set reg_status to 'invalid_credentials' on deregistration

In order for JS to power wash the device on deregistration, its device
registration status should be set to 'invalid_credentials.

BUG=brillo:1228
TEST=`FEATURES=test emerge-link buffet`
     `test_that -b link <ip> e:buffet_.*`

Change-Id: I2b55e5948b57cb8b7f3746378b7479046fd8f00a
Reviewed-on: https://chromium-review.googlesource.com/282385
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: Vitaly Buka <vitalybuka@chromium.org>
Reviewed-by: Aaron Kemp <kemp@google.com>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
1 file changed
tree: 06e80f9d96dca592f1bf219624da8e4cd16d6203
  1. buffet/