Case logic in `saltmod.py:function` fails to handle ssh permsision denied

Description of Issue

Typical mdata coming back from permission denied on an ssh attempt on a minion looks as follows:

{'stdout': "ubuntu@10.42.1.154's password: \nubuntu@10.42.1.154's password: \nubuntu@10.42.1.154's password: \n", 'stderr': "Warning: Permanently added '10.42.1.154' (ECDSA) to the list of known hosts.\r\nPermission denied, please try again.\r\nPermission denied, please try again.\r\nubuntu@10.42.1.154: Permission denied (publickey,password).\r\n", 'retcode': 255}

Meanwhile, saltmod.py:function implements the following logic:
https://github.com/saltstack/salt/blob/e683178e37640b0be3ebbd6029e33172505144ab/salt/states/saltmod.py#L600-L619

The result is:

[DEBUG   ] An exception occurred in this state: 'ret'
Traceback (most recent call last):
  File "/home/f0cal/_venv/lib/python3.6/site-packages/salt/state.py", line 1933, in call
    **cdata['kwargs'])
  File "/home/f0cal/_venv/lib/python3.6/site-packages/salt/loader.py", line 1951, in wrapper
    return f(*args, **kwargs)
  File "/home/f0cal/_venv/lib/python3.6/site-packages/salt/states/saltmod.py", line 554, in function
    m_ret = mdata['ret']
KeyError: 'ret'
[ERROR   ] An exception occurred in this state: Traceback (most recent call last):
  File "/home/f0cal/_venv/lib/python3.6/site-packages/salt/state.py", line 1933, in call
    **cdata['kwargs'])
  File "/home/f0cal/_venv/lib/python3.6/site-packages/salt/loader.py", line 1951, in wrapper
    return f(*args, **kwargs)
  File "/home/f0cal/_venv/lib/python3.6/site-packages/salt/states/saltmod.py", line 554, in function
    m_ret = mdata['ret']
KeyError: 'ret'

The logic is clearly failing to handle the case where there's a nonzero retcode without a corresponding minion return in the blob.

Setup

Steps to Reproduce Issue

Versions Report

Salt Version:
           Salt: 2019.2.1
 
Dependency Versions:
           cffi: 1.12.3
       cherrypy: Not Installed
       dateutil: 2.8.0
      docker-py: Not Installed
          gitdb: Not Installed
      gitpython: Not Installed
          ioflo: Not Installed
         Jinja2: 2.10.1
        libgit2: Not Installed
        libnacl: Not Installed
       M2Crypto: Not Installed
           Mako: Not Installed
   msgpack-pure: Not Installed
 msgpack-python: 0.6.2
   mysql-python: Not Installed
      pycparser: 2.19
       pycrypto: 2.6.1
   pycryptodome: Not Installed
         pygit2: Not Installed
         Python: 3.6.8 (default, Aug 20 2019, 17:12:48)
   python-gnupg: Not Installed
         PyYAML: 4.2
          PyZMQ: 18.1.0
           RAET: Not Installed
          smmap: Not Installed
        timelib: Not Installed
        Tornado: 4.5.3
            ZMQ: 4.3.2
 
System Versions:
           dist: Ubuntu 18.04 bionic
         locale: UTF-8
        machine: x86_64
        release: 4.15.0-64-generic
         system: Linux
        version: Ubuntu 18.04 bionic

Start in salt/states/saltmod.py:function around the linked lines and inspect how the mdata dictionary is handled when retcode is nonzero but ret is absent. Reproduce with the permission-denied mdata shown in the issue; done means the state reports the SSH failure without raising KeyError.