fix (接口测试): 修复自定义变量为全路径，环境中不配置url信息执行多出http:/

--bug=1008494 --user=赵勇 [github#8244] url不能完全使用环境变量或参数形式 https://www.tapd.cn/55049933/s/1077354

backend/src/main/java/org/apache/jmeter/protocol/http/sampler/HTTPSamplerProxy.java

@@ -112,6 +112,9 @@ public final class HTTPSamplerProxy extends HTTPSamplerBase implements Interrupt
         }
         try {
             String url = toExternalForm(u);
+            if (StringUtils.isNotEmpty(url) && url.startsWith("http:/http")) {
+                url = url.substring(6);
+            }
             u = new URL(url);
         } catch (Exception ex) {
             LogUtil.error(ex);