Add hacky sleep trying to mitigate the test flakiness for now

[chizhg]

No description provided.

[chizhg]

/uncc @evankanderson
/uncc @n3wscott

[chizhg]

/test pull-knative-eventing-integration-tests

[chizhg]

/test pull-knative-eventing-integration-tests

[chizhg]

/test pull-knative-eventing-integration-tests

[chizhg]

/cc @Harwayne
Looks it helps. 3/4 passed and the only failure was due to some cluster setup issue, which I've never met before.

[Harwayne]

/lgtm
/approve

For context, the continuous started going flaky red around da72a31 (#1119). We don't see any great reasons. The one that we looked into deeply had an error of:

 {"level":"error","ts":"2019-05-02T16:39:36.857Z","caller":"fanout/fanout_handler.go:121","msg":"Fanout had an error","error":"Unable to complete request Post http://e2e-singleevent-logger-pod-structured.test-single-structured-event-in-memory.svc.cluster.local/: dial tcp 10.43.246.111:80: i/o timeout","stacktrace":"github.com/knative/eventing/pkg/sidecar/fanout.(*Handler).dispatch\n\t/go/src/github.com/knative/eventing/pkg/sidecar/fanout/fanout_handler.go:121\ngithub.com/knative/eventing/pkg/sidecar/fanout.createReceiverFunction.func1\n\t/go/src/github.com/knative/eventing/pkg/sidecar/fanout/fanout_handler.go:99\ngithub.com/knative/eventing/pkg/provisioners.(*MessageReceiver).HandleRequest\n\t/go/src/github.com/knative/eventing/pkg/provisioners/message_receiver.go:155\ngithub.com/knative/eventing/pkg/sidecar/fanout.(*Handler).ServeHTTP\n\t/go/src/github.com/knative/eventing/pkg/sidecar/fanout/fanout_handler.go:104\ngithub.com/knative/eventing/pkg/sidecar/multichannelfanout.(*Handler).ServeHTTP\n\t/go/src/github.com/knative/eventing/pkg/sidecar/multichannelfanout/multi_channel_fanout_handler.go:105\ngithub.com/knative/eventing/pkg/sidecar/swappable.(*Handler).ServeHTTP\n\t/go/src/github.com/knative/eventing/pkg/sidecar/swappable/swappable.go:107\nnet/http.serverHandler.ServeHTTP\n\t/usr/local/go/src/net/http/server.go:2774\nnet/http.(*conn).serve\n\t/usr/local/go/src/net/http/server.go:1878"}

We aren't sure of the real root cause, but the idea with this PR is to add back the time between when a pod is running and when it is expected to do its 'job'. We used to get this time for free while the istio-proxy container was setup.

This feels icky, but the number of failed test runs is too high to wait until we get a real fix.

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This pull-request has been approved by: Fredy-Z, Harwayne

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