Add work-around for ssh pty race condition.

This should minimize loss of stdout when using
a pty and connecting with ssh or paramiko_ssh.

(cherry picked from commit bad293ae35)

lib/ansible/plugins/action/__init__.py

@@ -708,6 +708,9 @@ class ActionBase(with_metaclass(ABCMeta, object)):
         if self._connection.allow_executable:
             if executable is None:
                 executable = self._play_context.executable
+                # mitigation for SSH race which can drop stdout (https://github.com/ansible/ansible/issues/13876)
+                # only applied for the default executable to avoid interfering with the raw action
+                cmd = self._connection._shell.append_command(cmd, 'sleep 0')
             if executable:
                 cmd = executable + ' -c ' + pipes.quote(cmd)
 

lib/ansible/plugins/shell/__init__.py

@@ -171,3 +171,11 @@ class ShellBase(object):
         if rm_tmp:
             new_cmd = '%s; rm -rf "%s" %s' % (new_cmd, rm_tmp, self._SHELL_REDIRECT_ALLNULL)
         return new_cmd
+
+    def append_command(self, cmd, cmd_to_append):
+        """Append an additional command if supported by the shell"""
+
+        if self._SHELL_AND:
+            cmd += ' %s %s' % (self._SHELL_AND, cmd_to_append)
+
+        return cmd