Fix parsing of tasks with variable module names

Also adding an integration test for same.

test/integration/roles/test_good_parsing/tasks/main.yml

@@ -152,4 +152,15 @@
     that:
       - complex_param == "this is a param in a complex arg with double quotes"
 
+- name: test variable module name
+  action: "{{ variable_module_name }} msg='this should be debugged'"
+  register: result
+
+- debug: var=result
+
+- name: assert the task with variable module name ran
+  assert:
+    that:
+      - result.invocation.module_name == "debug"
+      - result.msg == "this should be debugged"
 

test/integration/roles/test_good_parsing/vars/main.yml

@@ -0,0 +1,2 @@
+---
+variable_module_name: debug