(FACT-546) Enclose interface name in single quotes

oVirt/RHEV creates a ";vdsmdummy;" network interface. 

facter outputs many messages: 
sh: vdsmdummy: command not found

ifconfig and ip command lines are called like "/sbin/ifconfig ;vdsmdummy;" which is interpreted as "ifconfig" and "vdsmdummy" (same for the ip command). 

The interface names should be enclosed by single quotes.