HADOOP-17294. Fix typos existance to existence (#2357)

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/jobhistory/JobHistoryEventHandler.java

@@ -227,7 +227,7 @@ public class JobHistoryEventHandler extends AbstractService
       }
       }
     } catch (IOException e) {
-      LOG.error("Failed checking for the existance of history intermediate " +
+      LOG.error("Failed checking for the existence of history intermediate " +
       		"done directory: [" + doneDirPath + "]");
       throw new YarnRuntimeException(e);
     }

hadoop-tools/hadoop-archive-logs/src/site/markdown/HadoopArchiveLogs.md

@@ -59,7 +59,7 @@ How to Archive Logs
     -verbose                       Print more details.
 
 The tool only supports running one instance on a cluster at a time in order
-to prevent conflicts. It does this by checking for the existance of a
+to prevent conflicts. It does this by checking for the existence of a
 directory named ``archive-logs-work`` under
 ``yarn.nodemanager.remote-app-log-dir`` in HDFS
 (default: ``/tmp/logs/archive-logs-work``). If for some reason that