Update getting-started.md

/usr/share/zoneinfo/ has older names for some timezones. Creating the link did not work for me since the name of my timezone has changed from Asia/Calcutta to Asia/Kolkata. timedatectl works perfectly well on CentOS7 and seems like a better way of setting the timezone.
Merge pull request #89 from 9rj/patch-1

Update getting-started.md