Replace fmt.Sprintf() with labels.NewSelector() for building labelselectors

[savitaashture]

Changes

Fixes: #593

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Release Notes

Use labels.NewSelector() for building labelselectors

[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-operator-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/reconciler/common/labels.go	Do not exist	88.9%

[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-operator-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/reconciler/common/labels.go	Do not exist	85.7%

[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-operator-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/reconciler/common/labels.go	Do not exist	85.7%

[tekton-robot]

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