Revert "Enable host_key checking at the strategy level"

This reverts commit 1a6d660d7e285cceec474952a33af4d8dffd0a8d.

lib/ansible/executor/task_executor.py

@@ -32,7 +32,6 @@ from ansible.errors import AnsibleError, AnsibleParserError, AnsibleUndefinedVar
 from ansible.playbook.conditional import Conditional
 from ansible.playbook.task import Task
 from ansible.template import Templar
-from ansible.utils.connection import get_smart_connection_type
 from ansible.utils.encrypt import key_for_hostname
 from ansible.utils.listify import listify_lookup_plugin_terms
 from ansible.utils.unicode import to_unicode
@@ -565,7 +564,21 @@ class TaskExecutor:
 
         conn_type = self._play_context.connection
         if conn_type == 'smart':
-            conn_type = get_smart_connection_type(self._play_context)
+            conn_type = 'ssh'
+            if sys.platform.startswith('darwin') and self._play_context.password:
+                # due to a current bug in sshpass on OSX, which can trigger
+                # a kernel panic even for non-privileged users, we revert to
+                # paramiko on that OS when a SSH password is specified
+                conn_type = "paramiko"
+            else:
+                # see if SSH can support ControlPersist if not use paramiko
+                try:
+                    cmd = subprocess.Popen(['ssh','-o','ControlPersist'], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+                    (out, err) = cmd.communicate()
+                    if "Bad configuration option" in err or "Usage:" in err:
+                        conn_type = "paramiko"
+                except OSError:
+                    conn_type = "paramiko"
 
         connection = self._shared_loader_obj.connection_loader.get(conn_type, self._play_context, self._new_stdin)
         if not connection: