state.low: KeyError: '__id__'

Description of Issue/Question

state.low expects an explicit __id__.

Setup

CentOS 7; salt installed with bootstrap script.

Steps to Reproduce Issue

The documentation of state.low suggests the following should work:

[root@salt salt]# salt salt\* state.low '{"state": "file", "fun": "exists", "name": "/etc/fstab"}'
salt.localdomain:
    The minion function caused an exception: Traceback (most recent call last):
      File "/usr/lib/python2.7/site-packages/salt/minion.py", line 1470, in _thread_return
        return_data = executor.execute()
      File "/usr/lib/python2.7/site-packages/salt/executors/direct_call.py", line 28, in execute
        return self.func(*self.args, **self.kwargs)
      File "/usr/lib/python2.7/site-packages/salt/modules/state.py", line 312, in low
        ret = st_.call(data)
      File "/usr/lib/python2.7/site-packages/salt/state.py", line 1901, in call
        ret['__id__'] = low['__id__']
    KeyError: '__id__'
[root@salt salt]#

However it does not because no explicit __id__ is added. The state compiler explicitly references this key since https://github.com/saltstack/salt/pull/26780.

So either the documentation needs to be updated to reflect the need to explicitly pass __id__, or State.call() needs to handle it being absent.

Also, tests for state.low have not caught this for some reason.

Versions Report

Salt Version:
           Salt: 2017.7.2

Dependency Versions:
           cffi: Not Installed
       cherrypy: Not Installed
       dateutil: Not Installed
      docker-py: Not Installed
          gitdb: Not Installed
      gitpython: Not Installed
          ioflo: Not Installed
         Jinja2: 2.7.2
        libgit2: Not Installed
        libnacl: Not Installed
       M2Crypto: Not Installed
           Mako: Not Installed
   msgpack-pure: Not Installed
 msgpack-python: 0.4.8
   mysql-python: Not Installed
      pycparser: Not Installed
       pycrypto: 2.6.1
   pycryptodome: Not Installed
         pygit2: Not Installed
         Python: 2.7.5 (default, Aug  4 2017, 00:39:18)
   python-gnupg: Not Installed
         PyYAML: 3.11
          PyZMQ: 15.3.0
           RAET: Not Installed
          smmap: Not Installed
        timelib: Not Installed
        Tornado: 4.2.1
            ZMQ: 4.1.4

System Versions:
           dist: centos 7.4.1708 Core
         locale: ANSI_X3.4-1968
        machine: x86_64
        release: 3.10.0-693.11.6.el7.x86_64
         system: Linux
        version: CentOS Linux 7.4.1708 Core