Suppress notifications from modern mac testing.

This will avoid lots of notifications to regressions list. This should be
reverted once the nondeterministic failures are fixed.
Merge pull request #344 from thomasvandoren/new-mac-suppress-spammy-notifications

Suppress notifications from modern mac testing.

This will avoid lots of notifications to regressions list. This should be
reverted once the nondeterministic failures are fixed.