The command 'test' is similar to the
command 'status' but instead of displaying
the status, it returns a status: 0 if smackFS
is mounted or 1 otherwise.

The intention is to provide a cleaner interface
for scripting. Instead of writing

 if smackctl status | grep -qv ' not '; then ...

the script progreammer can simply write

 if smackctl test; then ...

Signed-off-by: José Bollo <jose.bollo@iot.bzh>