vfs: Adjust fsinfo sample output

Adjust the output of the test-fsinfo sample program to:

 (1) Print server addresses if of AF_INET or AF_INET6 family.

 (2) Not print parameter descriptions (the test-fs-query sample program can
     be used for that).

 (3) Only print non-blank parameter values so that parameters that just
     encode defaults don't clutter up the output.

Signed-off-by: David Howells <dhowells@redhat.com>