Force ntp panic off

Panic should be off for virtual machines [1]. However, facter isn't
picking up that our machines are virtual.

[1]
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1006427
Merge pull request #607 from alphagov/upgrade-ntp-again

Force ntp panic off