Added NTP support for windows.

Added the support for storing the NTP server information on windows platform.
Fixed the case of empty NTP list

If there is no NTP server, do not set any default.
Merge pull request #32 from ociuhandu/pull-req-release-pebbles-master-58a2078e8676eb14d4439f36e1ad3e1385f0a21b

https://github.com/crowbar/barclamp-ntp/pull/32

Merged by devtool for VictorLowther