Virtual environment not activated when debugging in WSL

[DonJayamanne]

Description

While using the Remote - WSL, the Python extension fails to activate the venv on new integrated terminals.
Python Extension does recognize the venv when debugging.

Steps to reproduce

1. Open insiders from a WSL folder code-insiders .. The Remote - WSL is installed automatically.
2. Install Python extension on in insiders WSL.
3. Reload window
4. Open terminal, create a venv python3.7 -m venv venv
5. Select venv's python as the interpreter
6. Select a python file
7. Close/open an integrated terminal
8. Venv is not automatically activated

Expected results:

The command . venv/bin/activate should be automatically issued in the integrated terminal.

Actual results

The venv is not automatically activated

Originally reported here microsoft/vscode-remote-release#368

[DonJayamanne]

Closing as a duplicate of #5743