test_list_servers_by_admin for preexisting servers

test_list_servers_by_admin has been implemented by corresponding to
test_list_servers_by_admin_with_all_tenants which specifies an option
all_tenants. As the bug report, test_list_servers_by_admin expected
admin user should not have any pre-existing servers, but it is possible
on some clouds.
As the original purpose of test_list_servers_by_admin, it is fine to
verify the server list doesn't contain the other tenants' servers.
Then this patch changes test_list_servers_by_admin to do that.
In addition, this patch moves test_list_servers_by_admin to next to
test_list_servers_by_admin_with_all_tenants for comparing them easily.

Change-Id: I4ba5bedef154c1313b6c60f24f177ae3d9ac15ef
Closes-Bug: #1295369
1 file changed