Drain response body properly for http connection pool (#6415)

Currently Go http connection pool was not being properly
utilized leading to degrading performance as the number
of concurrent requests increased.

As recommended by Go implementation, we have to drain the
response body and close it.

pkg/madmin/config-commands.go

@@ -85,7 +85,7 @@ func (adm *AdminClient) GetConfig() ([]byte, error) {
 	if resp.StatusCode != http.StatusOK {
 		return nil, httpRespToErrorResponse(resp)
 	}
-	defer resp.Body.Close()
+	defer closeResponse(resp)
 
 	return DecryptServerConfigData(adm.secretAccessKey, resp.Body)
 }