Elasticsearch version: 5.1.1

Plugins installed: [x-pack]

JVM version:

openjdk version "1.8.0_111"
OpenJDK Runtime Environment (build 1.8.0_111-b15)
OpenJDK 64-Bit Server VM (build 25.111-b15, mixed mode)

OS version:
RHEL 7.2

Description of the problem including expected versus actual behavior:
Followed steps Install Elasticsearch with .zip or .tar.gz
Steps to reproduce:

1. Install OpenJDK [java-1.8.0-openjdk]
2. Unarchived elasticsearch binary to install location
3. Change install location ownership to unique user and group [elkusr:elkgrp]
4. Update /etc/security/limits.conf
   • 'elkusr - nofile 65536'
   • 'elkusr soft memlock unlimited'
   • 'elkusr hard memlock unlimited'
   • 'elkusr soft nproc 2048'
   • 'elkusr hard nproc 2048'
5. Update /etc/sysctl.conf and reload systemctl
   • 'vm.max_map_count = 262144'
   • 'vm.swappiness = 0'
6. Installed x-pack plugin from binary
   • elasticsearch/bin/elasticsearch-plugin install file:///tmp/x-pack-5.1.1.zip
7. Update elasticsearch.yml configuration
   • cluster.name: "elk_cluster"
   • node.name: "test_vm_1"
   • path.data: "/var/data/elasticsearch"
   • path.logs: "/var/log/elasticsearch"
   • bootstrap.memory_lock: true
   • network.host: "10.100.0.5"
   • discovery.zen.ping.unicast.hosts: ["test_vm_1", "test_vm_2"]
   • discovery.zen.minimum_master_nodes: 2
8. no change done to jvm.options or log4j.properties config.
9. Create service for elasticsearch
   • /etc/systemd/system/elasticsearch.service
10. Start elasticsearch service
    Provide logs (if relevant):
    elasticsearch created no logs for this.

service elasticsearch status
Redirecting to /bin/systemctl status  elasticsearch.service
● elasticsearch.service - Elasticsearch
   Loaded: loaded (/etc/systemd/system/elasticsearch.service; enabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Wed 2017-01-11 13:51:09 NZDT; 1s ago
     Docs: http://www.elastic.co
  Process: 26496 ExecStart=/opt/elasticsearch/bin/elasticsearch -Des.pidfile=${PID_DIR}/elasticsearch.pid -Des.default.path.home=${ES_HOME} -Des.default.path.logs=${LOG_DIR} -Des.default.path.data=${DATA_DIR} -Des.default.path.conf=${CONF_DIR} (code=exited, status=64)
 Main PID: 26496 (code=exited, status=64)

I even tried to execute elasticsearch directly, I got this warning and stopped:

/opt/elasticsearch/bin/elasticsearch
OpenJDK 64-Bit Server VM warning: If the number of processors is expected to increase from one, then you should configure the number of parallel GC threads appropriately using -XX:ParallelGCThreads=N

Any advise?