fix get fqdn

you can not simple check if ```socket.gethostname()``` returns a string with a dot. 

A hostname can have a dot in its name and still not be FQDN!
This patch will return the socket.fqhostname() if it's longer then the socket.hostname().

I created this patch because my minions on first starting are resolving the /etc/salt/minion_id as the hostname not the FQDN.  Many of our hostnames have dots in them.