AWS.CodeArtifact.NuGet.CredentialProvider does not work when DOTNET_CLI_HOME is set

**Describe the bug**

When `DOTNET_CLI_HOME` is set and AWS.CodeArtifact.NuGet.CredentialProvider is installed then the nuget plugin is installed to the wrong location.
It is installed to `$HOME/.nuget/plugins` but it should be `$DOTNET_CLI_HOME/.nuget/plugins`

**To Reproduce**
1. Set `DOTNET_CLI_HOME` to an empty folder
2. `dnx -y AWS.CodeArtifact.NuGet.CredentialProvider install`
3. Observe the log output: The nuget plugin is installed to $HOME/.nuget/plugins
4. Try to use an authenticated nuget feed from CodeArtifact
5. Observe that you get an error that you are not authenticated
6. Copy $HOME/.nuget/plugins to $DOTNET_CLI_HOME/.nuget/plugins
7. Observe that it now works

**Expected behavior**
AWS.CodeArtifact.NuGet.CredentialProvider installs the nuget plugin to the correct location

Start by reproducing the issue with DOTNET_CLI_HOME set to an empty folder and running `dnx -y AWS.CodeArtifact.NuGet.CredentialProvider install`; trace the plugin installation path from that entry point. Done means the plugin is placed under `$DOTNET_CLI_HOME/.nuget/plugins` and an authenticated CodeArtifact NuGet feed works without copying files manually.

Written by the indexing model from the issue text.