Send a mail to bazel-ci@ with the report of the global post-submit
Send a mail to bazel-ci@ with the report of the global post-submit

With that config the global post submit only send two mails at most
(and not a mail for every downstream job). And send one mail with
the actual report of A/B testing.

Change-Id: I1d514366f0e51648e04735db30bff0b5f622f6d4

bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration