Fix SSH slow login issue in RHEL7/OL7

Setting highlighted in green are final setting modified in sshd_conf.

[root@localhost ~]# diff /etc/ssh/sshd_config /etc/ssh/sshd_config.20160506
93,94c93,94
< #GSSAPIAuthentication yes
< #GSSAPICleanupCredentials no
---
> GSSAPIAuthentication yes
> GSSAPICleanupCredentials no
129c129
< UseDNS no
---
> #UseDNS yes

[root@localhost ~]# service sshd restart
Redirecting to /bin/systemctl restart  sshd.service

Reference URL: http://ask.xmodulo.com/fix-slow-ssh-login-issue-linux.html