[sonic test] introduce a repeat harness (#402)

* [sonic test] introduce a repeat harness

Introduce a test harness that repeats a user defined task list n times.

By default, n is 10, user can override n with
  -extra-vars 'test_iterations=<num>'

* Remove the iteration counter, it messes up some tests

* [repeat harness] remove repeat harness from test by tags

* [test cases] introduce repeat capability to test by testcase name

- Allowing a test case being repeated count.
- Keep testcase repeat harness for repeating a list of tasks

Author: yxieca

ansible/roles/test/tasks/repeat_harness.yml

@@ -0,0 +1,16 @@
+##########################################################################
+# Repeat harness is used to repeat a list of tasks, for single test case #
+#     repeatation, we can use repeat_count in test by testcase name      #
+#     infrastructure. This test case is the template for repeat a list   #
+#     of test cases, or run a test with delay between iterations. etc.   #
+##########################################################################
+
+- debug:
+    msg: "===================== Repeating starts ======================"
+
+# Add tasks here to be repeated:
+# e.g. - include: reboot.yml
+
+
+- debug:
+    msg: "===================== Repeating ends   ======================"

ansible/roles/test/tasks/test_sonic_by_testname.yml

@@ -27,11 +27,17 @@
         - sonic_hwsku in mellanox_hwskus
         - dscp_mode is not defined
 
+    - name: Set test repeat count
+      set_fact:
+          repeat_count: 1
+      when: repeat_count is not defined
+
 - debug: var=testcases[testcase_name]['execvars']
   when: testcases[testcase_name]['execvars'] is defined
 
-- name: run test case {{ testcases[testcase_name]['filename'] }} file
+- name: run test case {{ testcases[testcase_name]['filename'] }} file {{ repeat_count }} time(s)
   include: "{{ testcases[testcase_name]['filename'] }}"
+  with_sequence: end={{ repeat_count }}
 
 - debug: msg="!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
 - debug: msg="!!!!!!!!!!!!!!!!!!!! end running test {{ testcase_name }} !!!!!!!!!!!!!!!!!!!!"

ansible/roles/test/vars/testcases.yml

@@ -1,4 +1,8 @@
 testcases:
+    repeat_harness:
+      filename: repeat_harness.yml
+      topologies: [t0, t0-64, t0-64-32,t0-116, t1, t1-lag, t1-64-lag, ptf32, ptf64]
+
     acl: 
       filename: acl.yml
       topologies: [t1, t1-lag, t1-64-lag]