Correct multiple DNS servers and tolerate missing NTP
Correct multiple DNS servers and tolerate missing NTP

Multiple DNS servers in astute.yaml were not valid input
in the UI because they were missing a comma.

NTP config from system tests removes NTP2 and NTP3 servers.
Modified nailgun settings to permit empty NTP server
configuration.

Change-Id: Ie316e37817e889553840f4923d1426cb54e1589c
Closes-Bug: #1449026

ddepaoli3/fuel-library-dev,stackforge/fuel-library,stackforge/fuel-library,huntxu/fuel-library,xarses/fuel-library,eayunstack/fuel-library,ddepaoli3/fuel-library-dev,stackforge/fuel-library,huntxu/fuel-library,huntxu/fuel-library,ddepaoli3/fuel-library-dev,ddepaoli3/fuel-library-dev,eayunstack/fuel-library,eayunstack/fuel-library,xarses/fuel-library,xarses/fuel-library,eayunstack/fuel-library,stackforge/fuel-library,xarses/fuel-library,eayunstack/fuel-library,huntxu/fuel-library,ddepaoli3/fuel-library-dev,huntxu/fuel-library