build: use `dontcare` for flaky tests in Travis
Refs: https://github.com/nodejs/node/pull/27002#issuecomment-478256728
cc @addaleax
Checklist
-
make -j4 test(UNIX), orvcbuild test(Windows) passes -
commit message follows commit guidelines
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Refs: https://github.com/nodejs/node/pull/27002#issuecomment-478256728
cc @addaleax
make -j4 test (UNIX), or vcbuild test (Windows) passes