RATIS-2274. Newly added peer may retain outdated configuration after membership change, causing election failure. (#1246)

Author: RkGrit

ratis-server/src/main/java/org/apache/ratis/server/impl/LeaderStateImpl.java

@@ -799,6 +799,7 @@ private BootStrapProgress checkProgress(FollowerInfo follower, long committed) {
           follower.getLastRpcResponseTime().elapsedTimeMs());
       return BootStrapProgress.NOPROGRESS;
     } else if (follower.getMatchIndex() + stagingCatchupGap > committed
+        && follower.getMatchIndex() >= server.getRaftConf().getLogEntryIndex()
         && follower.getLastRpcResponseTime().compareTo(progressTime) > 0
         && follower.hasAttemptedToInstallSnapshot()) {
       return BootStrapProgress.CAUGHTUP;