Revert "Clear 'connection related' plugin vars for next loop iteration (#59024)"

This reverts commit 5e7e9b57c0.

This causes a new set of regressions from 2.8.2:
https://github.com/ansible/ansible/pull/59284#issuecomment-514021543

So this issue won't be fixed in 2.8.3 but work towards a fix for 2.8.4
will continue.

changelogs/fragments/58876-do-not-reuse-remote_user-from-prev-loop.yaml

@@ -1,2 +0,0 @@
-bugfixes:
-  - Do not re-use remote_user from previous loop iteration (https://github.com/ansible/ansible/issues/58876)

lib/ansible/executor/task_executor.py

@@ -410,20 +410,6 @@ class TaskExecutor:
             results.append(res)
             del task_vars[loop_var]
 
-            # clear 'connection related' plugin variables for next iteration
-            if self._connection:
-                clear_plugins = {
-                    'connection': self._connection._load_name,
-                    'shell': self._connection._shell._load_name
-                }
-                if self._connection.become:
-                    clear_plugins['become'] = self._connection.become._load_name
-
-                for plugin_type, plugin_name in iteritems(clear_plugins):
-                    for var in C.config.get_plugin_vars(plugin_type, plugin_name):
-                        if var in task_vars:
-                            del task_vars[var]
-
         self._task.no_log = no_log
 
         return results