brillo test: Only retry failed packages once.

The reasonning behind this is that the retry logic is here to avoid
failing the build when an explicit dependency is missing or a package
build is flaky (race condition, portage error, etc...).
As we run the unittests with the --nodeps option, we already expect this
command to choke if the dependencies are not correctly installed.
Moreover, if a developer runs the unit tests for a given package, a
failure is more likely due to a bug in the package than a bad dependency
or race condition and it is more useful to fail fast.

BUG=brillo:1011
TEST=`brillo test helloworld_base helloworld` exits after the first
failed emerge.

CQ-DEPEND=CL:271831
CQ-DEPEND=CL:272556

Change-Id: I331629f8de32179050298e2012acab713c381bb8
Reviewed-on: https://chromium-review.googlesource.com/272557
Trybot-Ready: Bertrand Simonnet <bsimonnet@chromium.org>
Tested-by: Bertrand Simonnet <bsimonnet@chromium.org>
Reviewed-by: Bertrand Simonnet <bsimonnet@chromium.org>
Commit-Queue: Bertrand Simonnet <bsimonnet@chromium.org>
2 files changed