Properly find e2e tests to run in the default runner (#375)
Properly find e2e tests to run in the default runner (#375)

Listing scripts to run using shell expansion fails if there are no scripts in `/test` (shell expansion won't occur, and the raw string will be interpreted as a script name). Use `find` instead, which can deal with this edge case.
knative/test-infra,knative/test-infra,knative/test-infra