HDDS-2053. Fix TestOzoneManagerRatisServer failure. Contributed by Xiaoyu Yao. (#1373)

hadoop-ozone/ozone-manager/src/test/java/org/apache/hadoop/ozone/om/ratis/TestOzoneManagerRatisServer.java

@@ -205,6 +205,7 @@ public class TestOzoneManagerRatisServer {
         .setOMServiceId(customOmServiceId)
         .build();
     // Starts a single node Ratis server
+    omRatisServer.stop();
     OzoneManagerRatisServer newOmRatisServer = OzoneManagerRatisServer
         .newOMRatisServer(newConf, ozoneManager, nodeDetails,
             Collections.emptyList());
@@ -219,6 +220,7 @@ public class TestOzoneManagerRatisServer {
     RaftGroupId raftGroupId = newOmRatisServer.getRaftGroup().getGroupId();
     Assert.assertEquals(uuid, raftGroupId.getUuid());
     Assert.assertEquals(raftGroupId.toByteString().size(), 16);
+    newOmRatisServer.stop();
   }