RATIS-2236 Fixed bug where manual triggerSnapshot would never finish (#1207)

Author: OneSizeFitsQuorum

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

@@ -216,6 +216,9 @@ private void waitForCommit() throws InterruptedException {
     // Thus it is possible to have applied > committed initially.
     final long applied = getLastAppliedIndex();
     for(; applied >= raftLog.getLastCommittedIndex() && state == State.RUNNING && !shouldStop(); ) {
+      if (server.getSnapshotRequestHandler().shouldTriggerTakingSnapshot()) {
+        takeSnapshot();
+      }
       if (awaitForSignal.await(100, TimeUnit.MILLISECONDS)) {
         return;
       }