##### SUMMARY
When using SSH against a Windows host with PowerShell v5 the stderr when pipelining is not being used contains a nested CLIXML message in the stderr. We should be able to handle this correctly and not fail.

Currently I can only explicitly disable pipelining for Windows as it should always be enabled but there is a report where this has happened in the wild so it's not unheard of https://github.com/ansible/awx/issues/6990.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
ssh
powershell

##### ANSIBLE VERSION
```paste below
devel
```

##### CONFIGURATION
Not sure yet, need to figure out how pipelining was disabled on the Windows case.

##### OS / ENVIRONMENT
Targeting Windows Server with PowerShell v5 and the SSH default shell is `powershell.exe`


##### STEPS TO REPRODUCE
Not sure yet, can only replicate by connecting to SSH on a WIndows host and manually changing https://github.com/ansible/ansible/blob/devel/lib/ansible/plugins/connection/ssh.py#L464 to False.

##### EXPECTED RESULTS
Works just fine


##### ACTUAL RESULTS
Fails because the stderr looks like (see nested CLIXML header)
```paste below
b'#< CLIXML\r\n#< CLIXML\r\n<Objs Version="1.1.0.1" xmlns="http://schemas.microsoft.com/powershell/2004/04"><Obj S="progress" RefId="0"><TN RefId="0"><T>System.Management.Automation.PSCustomObject</T><T>System.Object</T></TN><MS><I64 N="SourceId">1</I64><PR N="Record"><AV>Preparing modules for first use.</AV><AI>0</AI><Nil /><PI>-1</PI><PC>-1</PC><T>Completed</T><SR>-1</SR><SD> </SD></PR></MS></Obj></Objs><Objs Version="1.1.0.1" xmlns="http://schemas.microsoft.com/powershell/2004/04"><Obj S="progress" RefId="0"><TN RefId="0"><T>System.Management.Automation.PSCustomObject</T><T>System.Object</T></TN><MS><I64 N="SourceId">1</I64><PR N="Record"><AV>Preparing modules for first use.</AV><AI>0</AI><Nil /><PI>-1</PI><PC>-1</PC><T>Completed</T><SR>-1</SR><SD> </SD></PR></MS></Obj><Obj S="progress" RefId="1"><TNRef RefId="0" /><MS><I64 N="SourceId">2</I64><PR N="Record"><AV>Preparing modules for first use.</AV><AI>0</AI><Nil /><PI>-1</PI><PC>-1</PC><T>Completed</T><SR>-1</SR><SD> </SD></PR></MS></Obj></Objs>')
```

return substs[m.lastindex - 1]
        return re.sub(pattern, replace, value)
    def _encode_script(self, script, as_list=False, strict_mode=True, preserve_rc=True):
        '''Convert a PowerShell script to a single base64-encoded command.'''
        script = to_text(script)
        if script == u'-':
            cmd_parts = _common_args + ['-Command', '-']
        else:
            if strict_mode:
                script = u'Set-StrictMode -Version Latest\r\n%s' % script
            
            
            if preserve_rc:
                script = u'%s\r\nIf (-not $?) { If (Get-Variable LASTEXITCODE -ErrorAction SilentlyContinue) { exit $LASTEXITCODE } Else { exit 1 } }\r\n'\
                    % script
            script = '\n'.join([x.strip() for x in script.splitlines() if x.strip()])
            encoded_script = to_text(base64.b64encode(script.encode('utf-16-le')), 'utf-8')
            cmd_parts = _common_args + ['-EncodedCommand', encoded_script]
        if as_list:
            return cmd_parts
        return ' '.join(cmd_parts)