tests/ridalloc_exop: Add a new suite of tests for RID allocation

tests/ridalloc_exop: Add a new suite of tests for RID allocation

This moves some tests from getnc_exop.py regarding RID sets as well as
adding new tests for actions on join.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=9954

Pair-programmed-with: Clive Ferreira <cliveferreira@catalyst.net.nz>

Signed-off-by: Andrew Bartlett <abartlet@samaba.org>
Signed-off-by: Garming Sam <garming@catalyst.net.nz>
Signed-off-by: Clive Ferreira <cliveferreira@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>