Remove init checks for valid label and field selectors (influxdata#7198)

Importing k8s.io/klog starts a long running goroutine at init time.

docs/LICENSE_OF_DEPENDENCIES.md

@@ -163,8 +163,6 @@ following works:
 - gopkg.in/olivere/elastic.v5 [MIT License](https://github.com/olivere/elastic/blob/v5.0.76/LICENSE)
 - gopkg.in/tomb.v1 [BSD 3-Clause Clear License](https://github.com/go-tomb/tomb/blob/v1/LICENSE)
 - gopkg.in/yaml.v2 [Apache License 2.0](https://github.com/go-yaml/yaml/blob/v2.2.2/LICENSE)
-- k8s.io/apimachinery [Apache License 2.0](https://github.com/kubernetes/apimachinery/blob/master/LICENSE)
-- k8s.io/klog [Apache License 2.0](https://github.com/kubernetes/klog/blob/master/LICENSE)
 
 ## telegraf used and modified code from these projects
 - github.com/DataDog/datadog-agent [Apache License 2.0](https://github.com/DataDog/datadog-agent/LICENSE)

go.mod

@@ -138,7 +138,7 @@ require (
 	gopkg.in/olivere/elastic.v5 v5.0.70
 	gopkg.in/yaml.v2 v2.2.4
 	gotest.tools v2.2.0+incompatible // indirect
-	k8s.io/apimachinery v0.17.1
+	k8s.io/apimachinery v0.17.1 // indirect
 )
 
 // replaced due to https://github.com/satori/go.uuid/issues/73

plugins/inputs/prometheus/prometheus.go

@@ -15,8 +15,6 @@ import (
 	"github.com/influxdata/telegraf/internal"
 	"github.com/influxdata/telegraf/internal/tls"
 	"github.com/influxdata/telegraf/plugins/inputs"
-	"k8s.io/apimachinery/pkg/fields"
-	"k8s.io/apimachinery/pkg/labels"
 )
 
 const acceptHeader = `application/vnd.google.protobuf;proto=io.prometheus.client.MetricFamily;encoding=delimited;q=0.7,text/plain;version=0.0.4;q=0.3,*/*;q=0.1`
@@ -138,20 +136,6 @@ func (p *Prometheus) Init() error {
 		p.Log.Warnf("Use of deprecated configuration: 'metric_version = 1'; please update to 'metric_version = 2'")
 	}
 
-	if len(p.KubernetesLabelSelector) > 0 {
-		_, err := labels.Parse(p.KubernetesLabelSelector)
-		if err != nil {
-			return fmt.Errorf("label selector validation failed %q: %v", p.KubernetesLabelSelector, err)
-		}
-	}
-
-	if len(p.KubernetesFieldSelector) > 0 {
-		_, err := fields.ParseSelector(p.KubernetesFieldSelector)
-		if err != nil {
-			return fmt.Errorf("field selector validation failed %s: %v", p.KubernetesFieldSelector, err)
-		}
-	}
-
 	return nil
 }