Fixes #7263 - make sure the ip address from interfaces is valid

Both Fedora and PL packages carry it:

<pre>
$ rpm -qpR "http://yum.puppetlabs.com/el/7Server/products/x86_64/facter-2.2.0-1.el7.x86_64.rpm" | grep net-tools
net-tools
$ rpm -qpR "http://dl.fedoraproject.org/pub/epel/beta/7/x86_64/facter-2.0.1-2.el7.x86_64.rpm" | grep net-tools
net-tools
</pre>