HDFS-15932. Improve the balancer error message when process exits abnormally. Contributed by Renukaprasad C.

hadoop-common-project/hadoop-common/src/main/bin/hadoop-functions.sh

@@ -2205,7 +2205,7 @@ function hadoop_daemon_handler
       hadoop_verify_logdir
       hadoop_status_daemon "${daemon_pidfile}"
       if [[ $? == 0  ]]; then
-        hadoop_error "${daemonname} is running as process $(cat "${daemon_pidfile}").  Stop it first."
+        hadoop_error "${daemonname} is running as process $(cat "${daemon_pidfile}").  Stop it first and ensure ${daemon_pidfile} file is empty before retry."
         exit 1
       else
         # stale pid file, so just remove it and continue on
@@ -2266,7 +2266,7 @@ function hadoop_secure_daemon_handler
       hadoop_verify_logdir
       hadoop_status_daemon "${daemon_pidfile}"
       if [[ $? == 0  ]]; then
-        hadoop_error "${daemonname} is running as process $(cat "${daemon_pidfile}").  Stop it first."
+        hadoop_error "${daemonname} is running as process $(cat "${daemon_pidfile}").  Stop it first and ensure ${daemon_pidfile} file is empty before retry."
         exit 1
       else
         # stale pid file, so just remove it and continue on