netcmd: tests: test that create objects make use of addCleanup

netcmd: tests: test that create objects make use of addCleanup

Since the samdb connection is on the class and hangs around between tests, we need to clean up what we created.

Signed-off-by: Rob van der Linde <rob@catalyst.net.nz>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>