Fix nslookup cannot work well in initContainerTemplate

[hougangliu]

PytorchJob workers' initContainer always try to check if master pod is up by nslookup command, however nslookup in default image busybox:1.31.0 version seems too old that it cannot work well, its exit code is always 1 for ppc64le arch even it can parse master service dns, and for amd64, it cannot work steadily as below, when I change the image to alpine:3.10, both on amd64 and ppc64le, it works well

/ # nslookup katib-suggestion-hyperband
Server:         10.0.0.10
Address:        10.0.0.10:53

Name:   katib-suggestion-hyperband.kubeflow.svc.cluster.local
Address: 10.0.223.142

*** Can't find katib-suggestion-hyperband.svc.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.fyre.ibm.com: No answer
*** Can't find katib-suggestion-hyperband.kubeflow.svc.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.svc.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.fyre.ibm.com: No answer

/ # echo $?
0
/ # nslookup katib-suggestion-hyperband
Server:         10.0.0.10
Address:        10.0.0.10:53

** server can't find katib-suggestion-hyperband.kubeflow.svc.cluster.local: NXDOMAIN

*** Can't find katib-suggestion-hyperband.svc.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.fyre.ibm.com: No answer
*** Can't find katib-suggestion-hyperband.kubeflow.svc.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.svc.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.fyre.ibm.com: No answer

/ # echo $?
1
/ # nslookup katib-suggestion-hyperband
Server:         10.0.0.10
Address:        10.0.0.10:53

** server can't find katib-suggestion-hyperband.kubeflow.svc.cluster.local: NXDOMAIN

*** Can't find katib-suggestion-hyperband.svc.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.fyre.ibm.com: No answer
*** Can't find katib-suggestion-hyperband.kubeflow.svc.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.svc.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.fyre.ibm.com: No answer

/ # echo $?
1
/ # nslookup katib-suggestion-hyperband
Server:         10.0.0.10
Address:        10.0.0.10:53

Name:   katib-suggestion-hyperband.kubeflow.svc.cluster.local
Address: 10.0.223.142

*** Can't find katib-suggestion-hyperband.svc.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.fyre.ibm.com: No answer
*** Can't find katib-suggestion-hyperband.kubeflow.svc.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.svc.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.cluster.local: No answer
*** Can't find katib-suggestion-hyperband.fyre.ibm.com: No answer

/ # echo $?
0

[hougangliu]

/cc @johnugeorge

[gaocegege]

/lgtm
/assign @johnugeorge

[coveralls]

Coverage remained the same at 85.345% when pulling 7c7eeaf on hougangliu:fix-worker-init into c53647c on kubeflow:master.

[johnugeorge]

Thanks @hougangliu
/approve

[k8s-ci-robot]

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