k8s_audit: fix flaky windows test (#3940)

* k8s_audit: fix flaky windows test

On windows, immediately reusing a tcp port can lead to the observed
error. This commit randomizes the port number.

k8s-audit server failed: listen tcp 127.0.0.1:49234: bind: An attempt was made to access a socket in a way forbidden by its access permissions.

https://stackoverflow.com/questions/22549044/why-is-port-not-immediately-released-after-the-socket-closes

https://github.com/golang/go/issues/10527

* lint

* don't bother to ask for a free port, just give a different #

pkg/acquisition/modules/kubernetesaudit/k8s_audit_test.go

@@ -1,6 +1,7 @@
 package kubernetesauditacquisition
 
 import (
+	"fmt"
 	"net/http/httptest"
 	"strings"
 	"testing"
@@ -109,7 +110,6 @@ func TestHandler(t *testing.T) {
 	ctx := t.Context()
 	tests := []struct {
 		name               string
-		config             string
 		expectedStatusCode int
 		body               string
 		method             string
@@ -117,10 +117,6 @@ func TestHandler(t *testing.T) {
 	}{
 		{
 			name: "valid_json",
-			config: `source: k8s-audit
-listen_addr: 127.0.0.1
-listen_port: 49234
-webhook_path: /k8s-audit`,
 			method:             "POST",
 			expectedStatusCode: 200,
 			body: `
@@ -216,10 +212,6 @@ webhook_path: /k8s-audit`,
 		},
 		{
 			name: "invalid_json",
-			config: `source: k8s-audit
-listen_addr: 127.0.0.1
-listen_port: 49234
-webhook_path: /k8s-audit`,
 			expectedStatusCode: 500,
 			body:               "invalid json",
 			method:             "POST",
@@ -227,10 +219,6 @@ webhook_path: /k8s-audit`,
 		},
 		{
 			name: "invalid_method",
-			config: `source: k8s-audit
-listen_addr: 127.0.0.1
-listen_port: 49234
-webhook_path: /k8s-audit`,
 			expectedStatusCode: 405,
 			method:             "GET",
 			eventCount:         0,
@@ -239,7 +227,7 @@ webhook_path: /k8s-audit`,
 
 	subLogger := log.WithField("type", "k8s-audit")
 
-	for _, test := range tests {
+	for idx, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
 			out := make(chan types.Event)
 			tb := &tomb.Tomb{}
@@ -257,9 +245,17 @@ webhook_path: /k8s-audit`,
 			})
 
 			f := KubernetesAuditSource{}
-			err := f.UnmarshalConfig([]byte(test.config))
+
+			port := 49234+idx
+			config := fmt.Sprintf(`source: k8s-audit
+listen_addr: 127.0.0.1
+listen_port: %d
+webhook_path: /k8s-audit`, port)
+
+			err := f.UnmarshalConfig([]byte(config))
 			require.NoError(t, err)
-			err = f.Configure([]byte(test.config), subLogger, metrics.AcquisitionMetricsLevelNone)
+
+			err = f.Configure([]byte(config), subLogger, metrics.AcquisitionMetricsLevelNone)
 
 			require.NoError(t, err)