store/helper: use random server port in test (#14988)
store/helper: use random server port in test (#14988)


coocood/tidb,ngaut/tidb,coocood/tidb,pingcap/tidb,pingcap/tidb,c4pt0r/tidb,ngaut/tidb,kyle-wang/tidb,c4pt0r/tidb,XuHuaiyu/tidb,EvilMcJerkface/tidb,kyle-wang/tidb,ngaut/tidb,ngaut/tidb,kyle-wang/tidb,ngaut/tidb,pingcap/tidb,c4pt0r/tidb,ngaut/tidb,kyle-wang/tidb,c4pt0r/tidb,pingcap/tidb,kyle-wang/tidb,XuHuaiyu/tidb,EvilMcJerkface/tidb,c4pt0r/tidb,pingcap/tidb,kyle-wang/tidb,c4pt0r/tidb,pingcap/tidb