re-use transport for AdminInfo() call (#14571)

avoids creating new transport for each `isServerResolvable`
request, instead re-use the available global transport and do
not try to forcibly close connections to avoid TIME_WAIT
build upon large clusters.

Never use httpClient.CloseIdleConnections() since that can have
a drastic effect on existing connections on the transport pool.

Remove it everywhere.

internal/config/dns/operator_dns.go

@@ -155,7 +155,6 @@ func (c *OperatorDNS) DeleteRecord(record SrvRecord) error {
 
 // Close closes the internal http client
 func (c *OperatorDNS) Close() error {
-	c.httpClient.CloseIdleConnections()
 	return nil
 }
 

internal/config/identity/openid/jwt.go

@@ -471,7 +471,6 @@ func parseDiscoveryDoc(u *xnet.URL, transport *http.Transport, closeRespFn func(
 	}
 	resp, err := clnt.Do(req)
 	if err != nil {
-		clnt.CloseIdleConnections()
 		return d, err
 	}
 	defer closeRespFn(resp.Body)

internal/event/target/webhook.go

@@ -228,8 +228,6 @@ func (target *WebhookTarget) Send(eventKey string) error {
 
 // Close - does nothing and available for interface compatibility.
 func (target *WebhookTarget) Close() error {
-	// Close idle connection with "keep-alive" states
-	target.httpClient.CloseIdleConnections()
 	return nil
 }