Remove shell module specialcases

Shell is implemented via the command module.  There was a special case
in mod_args to do that.  Make shell into an action plugin to handle that
instead.

Also move the special case for the command nanny into a command module
action plugin.  This is more appropriate as we then do not have to send
a parameter that is only for the command module to every single module.

test/units/playbook/test_task.py

@@ -23,13 +23,13 @@ from ansible.compat.tests import unittest
 from ansible.playbook.task import Task
 
 
-basic_shell_task = dict(
+basic_command_task = dict(
     name='Test Task',
-    shell='echo hi'
+    command='echo hi'
 )
 
-kv_shell_task = dict(
-    action='shell echo hi'
+kv_command_task = dict(
+    action='command echo hi'
 )
 
 
@@ -54,20 +54,20 @@ class TestTask(unittest.TestCase):
         pass
 
     def test_load_task_simple(self):
-        t = Task.load(basic_shell_task)
+        t = Task.load(basic_command_task)
         assert t is not None
-        self.assertEqual(t.name, basic_shell_task['name'])
+        self.assertEqual(t.name, basic_command_task['name'])
         self.assertEqual(t.action, 'command')
-        self.assertEqual(t.args, dict(_raw_params='echo hi', _uses_shell=True))
+        self.assertEqual(t.args, dict(_raw_params='echo hi'))
 
     def test_load_task_kv_form(self):
-        t = Task.load(kv_shell_task)
+        t = Task.load(kv_command_task)
         self.assertEqual(t.action, 'command')
-        self.assertEqual(t.args, dict(_raw_params='echo hi', _uses_shell=True))
+        self.assertEqual(t.args, dict(_raw_params='echo hi'))
 
     def test_task_auto_name(self):
-        assert 'name' not in kv_shell_task
-        t = Task.load(kv_shell_task)
+        assert 'name' not in kv_command_task
+        t = Task.load(kv_command_task)
         # self.assertEqual(t.name, 'shell echo hi')
 
     def test_task_auto_name_with_role(self):