selftest: more dfree command and smbclient disk usage tests

selftest: more dfree command and smbclient disk usage tests

Add tests that cover disk usage printing by smbclient, as well
as passing directory info to the "dfree command" script.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11662

Signed-off-by: Uri Simchoni <uri@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Wed Jan  6 03:58:59 CET 2016 on sn-devel-144

(cherry picked from commit 3e1b26bd6d0998c3af3d77f94eaac469434389be)