selftest: add disk-free quota tests

selftest: add disk-free quota tests

Add a test for situation where quota accounting is enabled
but quota enforcement is disabled (disk-free should not take
quota into account)

Add a test for situation where overall quota status reporting
(whether or not it's enforcing) is not supported - as with NFS.
In that case it must be assumed that if quota is configured, then
it is also enforced (as with NFS).

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11937

Signed-off-by: Uri Simchoni <uri@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>