Use reader role in test_list_servers_negative

Update test_list_servers_negative.py to use the reader role for all
GET requests (list operations) following the pattern in
test_list_server_filters.py. This ensures proper RBAC testing by
using the project_reader credentials for read operations while
maintaining the primary credentials for write operations.

Partial-Implements: blueprint test-nova-with-srbac-defaults
Change-Id: I4be4395a538c59b3faca4abbf5baaf546accbd00
Signed-off-by: Jason Paroly <jparoly@redhat.com>
1 file changed