Fix the default LeaderElectionID and make it an argument

[goyalankit]

What this PR does / why we need it:
This PR fixes the default leader election ID which has an invalid format. If one enables leader election through leader-elect=true, the operator fails to start with the following error:

Before:

> go run ./cmd/training-operator.v1/main.go -leader-elect=true --namespace kubeflow
1.6589798403535447e+09  INFO    controller-runtime.metrics      Metrics server is starting to listen    {"addr": ":8080"}
1.6589798403555276e+09  INFO    setup   starting manager
1.6589798403558226e+09  INFO    Starting server {"path": "/metrics", "kind": "metrics", "addr": "[::]:8080"}
1.6589798403558557e+09  INFO    Starting server {"kind": "health probe", "addr": "[::]:8081"}
I0727 20:44:00.356108 1889297 leaderelection.go:248] attempting to acquire leader lease kubeflow/1ca428e5....
E0727 20:44:00.360526 1889297 leaderelection.go:334] error initially creating leader election record: Lease.coordination.k8s.io "1ca428e5." is invalid: metadata.name: Invalid value: "1ca428e5.": a lowercase RFC 1123 subdomain must consist of lower case alphanumeric characters, '-' or '.', and must start and end with an alphanumeric character (e.g. 'example.com', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*')
E0727 20:44:04.107669 1889297 leaderelection.go:334] error initially creating leader election record: Lease.coordination.k8s.io "1ca428e5." is invalid: metadata.name: Invalid value: "1ca428e5.": a lowercase RFC 1123 subdomain must consist of lower case alphanumeric characters, '-' or '.', and must start and end with an alphanumeric character (e.g. 'example.com', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*')

Fails to acquire lease:

E0727 20:44:04.107669 1889297 leaderelection.go:334] error initially creating leader election record: Lease.coordination.k8s.io "1ca428e5." is invalid: metadata.name: Invalid value: "1ca428e5.": a lowercase RFC 1123 subdomain must consist of lower case alphanumeric characters, '-' or '.', and must start and end with an alphanumeric character (e.g. 'example.com', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*')

After:

> go run ./cmd/training-operator.v1/main.go -leader-elect=true --namespace kubeflow
1.6589798807258694e+09  INFO    controller-runtime.metrics      Metrics server is starting to listen    {"addr": ":8080"}
1.6589798807272537e+09  INFO    setup   starting manager
1.6589798807275426e+09  INFO    Starting server {"path": "/metrics", "kind": "metrics", "addr": "[::]:8080"}
1.6589798807275436e+09  INFO    Starting server {"kind": "health probe", "addr": "[::]:8081"}
I0727 20:44:40.727719 1890098 leaderelection.go:248] attempting to acquire leader lease kubeflow/1ca428e5.training-operator.kubeflow.org...
I0727 20:44:57.469968 1890098 leaderelection.go:258] successfully acquired lease kubeflow/1ca428e5.training-operator.kubeflow.org
1.6589798974700997e+09  DEBUG   events  Normal  {"object": {"kind":"Lease","namespace":"kubeflow","name":"1ca428e5.training-operator.kubeflow.org","uid":"bea108c0-01ba-4759-bdd4-d55accfa7596","apiVersion":"coordination.k8s.io/v1","resourceVersion":"16304"}, "reason": "LeaderElection", "message": "angoyal-ld5.linkedin.biz_a24fbed3-c23d-4d3d-922b-407b342e23d8 became leader"}
1.6589798974702497e+09  INFO    Starting EventSource    {"controller": "mxjob-controller", "source": "kind source: *v1.MXJob"}
1.6589798974702735e+

Successfully acquires lease:

I0727 20:44:40.727719 1890098 leaderelection.go:248] attempting to acquire leader lease kubeflow/1ca428e5.training-operator.kubeflow.org... I0727 20:44:57.469968 1890098 leaderelection.go:258] successfully acquired lease kubeflow/1ca428e5.training-operator.kubeflow.org

Which issue(s) this PR fixes (optional, in Fixes #<issue number>, #<issue number>, ... format, will close the issue(s) when PR gets merged):
Fixes #1640

Checklist:

• Docs included if any changes are user facing

[gaocegege]

Thanks for the quick fix!

[gaocegege]

/ok-to-test

/lgtm
/approve

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gaocegege, goyalankit

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[coveralls]

Pull Request Test Coverage Report for Build 2751166096

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 6 unchanged lines in 1 file lost coverage.
• Overall coverage remained the same at 39.914%

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Files with Coverage Reduction	New Missed Lines	%
pkg/controller.v1/mpi/mpijob_controller.go	6	77.46%

Totals
Change from base Build 2735722547:	0.0%
Covered Lines:	2331
Relevant Lines:	5840

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💛 - Coveralls