nanoserver powershell image unable to use install-modules by default

[identifi-awilliamson]

Steps to reproduce

1. Pull the latest mcr.microsoft.com/powershell:lts-nanoserver-1809 image
2. Run a container in interactive mode using the image
3. Check the PSModulePath environment variable
4. Attempt to install a PSGallery module using Install-Module with -Verbose (module used in this case is powershell-yaml)
5. Notice the verbose output shows the install path a C:\Users\ContainerUser\Documents\Powershell\Modules
6. This path is not in the PSModulePath env variable

** Note attempting to run Install-Module with -Scope AllUsers fails due to permissions

docker pull mcr.microsoft.com/powershell:lts-nanoserver-1809

docker run -it --name=testModule mcr.microsoft.com/powershell:lts-nanoserver-1809

Install-Module powershell-yaml -SkipPublisherCheck -Scope CurrentUser -Verbose

Get-Module -ListAvailable

Expected behavior

The ContainerUser powershell module path should be in the PSModulePath env variable so that the installed module is available in both interactive container runs or for building images with modules packaged.

Actual behavior

The module installs but is not usable unless the PSModulePath env var is manipulated every session or as part of the image entrypoint, e.g. a script that first sets up the PSModulePath by hand then continues on to do whatever the image's intended work is. (We are currently doing this.)

Environment data

Client:
 Debug Mode: false

Server:
 Containers: 4
  Running: 1
  Paused: 0
  Stopped: 3
 Images: 18
 Server Version: 19.03.8
 Storage Driver: windowsfilter
  Windows:
 Logging Driver: json-file
 Plugins:
  Volume: local
  Network: ics internal l2bridge l2tunnel nat null overlay private transparent
  Log: awslogs etwlogs fluentd gcplogs gelf json-file local logentries splunk syslog
 Swarm: inactive
 Default Isolation: hyperv
 Kernel Version: 10.0 18362 (18362.1.amd64fre.19h1_release.190318-1202)
 Operating System: Windows 10 Pro Version 1903 (OS Build 18362.1082)
 OSType: windows
 Architecture: x86_64
 CPUs: 6
 Total Memory: 15.81GiB
 Name: IdentifiDOPaw
 ID: ZSX7:XQ5Y:XTMR:YNOD:3H47:GO5C:JCEO:YCLL:NPIR:OJHN:XZ7E:V7UB
 Docker Root Dir: C:\ProgramData\Docker
 Debug Mode: true
  File Descriptors: -1
  Goroutines: 45
  System Time: 2020-09-11T15:00:37.0752912-04:00
  EventsListeners: 1
 Registry: https://index.docker.io/v1/
 Labels:
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false
 Product License: Community Engine

Major  Minor  Patch  PreReleaseLabel BuildLabel
-----  -----  -----  --------------- ----------
7      0      3

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