CLOUDSTACK: 4705 - Fixed memory limits - domain limits test cases. Fixed attribute error

Signed-off-by: venkataswamybabu budumuru <venkataswamybabu.budumuru@citrix.com>
CLOUDSTACK-4747: Rename testcase name to use lesser characters

Renamed testcase name and also initialised _cleanup so that
it does not break on non-NS Cloudstack setup.

Signed-off-by: venkataswamybabu budumuru <venkataswamybabu.budumuru@citrix.com>
(cherry picked from commit c5e1c4725c3658cae967c63cbae0ffe598f227ef)