Revert "Revert "Stream logs from kube-task" (#233)"

[tdmanv]

This reverts commit e36c022, which remerges #228

Change Overview

• Prints logs from kube task pod as soon as they're ready in the controller
• Fixes some issues with WaitForPod* hanging

Issues

• Continuous logs from spawned commands #231

Pull request type

Please check the type of change your PR introduces:

• Work in Progress
• Refactoring (no functional changes, no api changes)
• Trival/Minor
• Bugfix
• Feature
• Documentation

Test Plan

/go/src/github.com/kanisterio/kanister # go test -v ./pkg/function -check.v -check.f TestKubeTask
=== RUN   Test
time="2019-08-29T01:21:55Z" level=info msg="Pod: kanister-job-vgzg4 Container: container Out: ###Phase-output###: {\"key\":\"version\",\"value\":\"0.21.0\"}"
time="2019-08-29T01:22:11Z" level=info msg="Pod: kanister-job-84vfl Container: container Out: Tick: 1"
time="2019-08-29T01:22:11Z" level=info msg="Pod: kanister-job-84vfl Container: container Out: Tick: 2"
time="2019-08-29T01:22:11Z" level=info msg="Pod: kanister-job-84vfl Container: container Out: Tick: 3"
PASS: kube_task_test.go:122: KubeTaskSuite.TestKubeTask 19.720s
OK: 1 passed
--- PASS: Test (20.03s)
PASS
ok      github.com/kanisterio/kanister/pkg/function     20.042s

• Manual
• Unit test
• E2E