fix the --fqdn no longer available in 3.8
fix the --fqdn no longer available in 3.8

This also makes the use of hostname -f consistent. Before there was use
of hostname -f and hostname --fqdn, after this change its only hostname
-f.

fixes #30

Signed-off-by: BlackEagle <6c5c99a37e4dd8841971a4b7c7580d6fcba68554@gmail.com>

maier/vagrant-alpine,maier/vagrant-alpine