test: use correct fqdn in passwd_sanitize()

test: use correct fqdn in passwd_sanitize()

My fqdn is 'natae.localdomain', however, socket.getfqdn() returns
'localhost'.

To fetch the true fqdn we need socket.getaddrinfo().

For more information see: https://stackoverflow.com/a/11580042/10474

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>