Reorganize integration tests:

- Move legacy tests into a separate directory.
- Reduce common dependencies between targets.

test/legacy/roles/netscaler_service/tasks/main.yaml

@@ -0,0 +1,2 @@
+---
+- { include: nitro.yaml, tags: ['nitro'] }

test/legacy/roles/netscaler_service/tasks/nitro.yaml

@@ -0,0 +1,14 @@
+- name: collect all nitro test cases
+  find:
+    paths: "{{ role_path }}/tests/nitro"
+    patterns: "{{ testcase }}.yaml"
+  register: test_cases
+
+- name: set test_items
+  set_fact: test_items="{{ test_cases.files | map(attribute='path') | list }}"
+
+- name: run test case
+  include: "{{ test_case_to_run }}"
+  with_items: "{{ test_items }}"
+  loop_control:
+    loop_var: test_case_to_run