Install openssh-client (Kaggle#971)

In Kaggle#967, I upgraded the base image from `m61` to `m64`.

The new  `m64` base image doesn't include a SSH client anymore.

This was causing issues with a learn course relying on `stable-baselines`. This package isn't included in our base image but is installed at runtime.

Install openssh-client (Kaggle#971)

In Kaggle#967, I upgraded the base image from `m61` to `m64`.

The new  `m64` base image doesn't include a SSH client anymore.

This was causing issues with a learn course relying on `stable-baselines`. This package isn't included in our base image but is installed at runtime.

Schedule build every day of the week. (Kaggle#959)

Starts 3 hours before the SDG daily build: https://github.com/Kaggle/shared-docker-graph-builder/blob/490eff4a2b34a22837a9a32df9c90733f562ce6d/Jenkinsfile#L4

Schedule build every day of the week. (Kaggle#959)

Starts 3 hours before the SDG daily build: https://github.com/Kaggle/shared-docker-graph-builder/blob/490eff4a2b34a22837a9a32df9c90733f562ce6d/Jenkinsfile#L4

Add pydot package (Kaggle#956)

This is used by keras plot_model() function.

Included a test to prevent regression.
Improved the existing tf test with extra assertions.

The issue was raised by a user here: https://www.kaggle.com/c/jane-street-market-prediction/discussion/214494#1184233

Add pydot package (Kaggle#956)

This is used by keras plot_model() function.

Included a test to prevent regression.
Improved the existing tf test with extra assertions.

The issue was raised by a user here: https://www.kaggle.com/c/jane-street-market-prediction/discussion/214494#1184233

Add flask. (Kaggle#946)

- Also added tests to prevent regression.

flask was removed from the base image we use:

```
rosbo@rosbo:~$ docker run -it --rm gcr.io/deeplearning-platform-release/base-cpu:m46 pip show flask
Name: Flask
Version: 1.1.2
Summary: A simple framework for building complex web applications.
Home-page: https://palletsprojects.com/p/flask/
Author: Armin Ronacher
Author-email: armin.ronacher@active-4.com
License: BSD-3-Clause
Location: /opt/conda/lib/python3.7/site-packages
Requires: Werkzeug, itsdangerous, click, Jinja2
Required-by:
rosbo@rosbo:~$ docker run -it --rm gcr.io/deeplearning-platform-release/base-cpu:m61 pip show flask
WARNING: Package(s) not found: flask
```

Add flask. (Kaggle#946)

- Also added tests to prevent regression.

flask was removed from the base image we use:

```
rosbo@rosbo:~$ docker run -it --rm gcr.io/deeplearning-platform-release/base-cpu:m46 pip show flask
Name: Flask
Version: 1.1.2
Summary: A simple framework for building complex web applications.
Home-page: https://palletsprojects.com/p/flask/
Author: Armin Ronacher
Author-email: armin.ronacher@active-4.com
License: BSD-3-Clause
Location: /opt/conda/lib/python3.7/site-packages
Requires: Werkzeug, itsdangerous, click, Jinja2
Required-by:
rosbo@rosbo:~$ docker run -it --rm gcr.io/deeplearning-platform-release/base-cpu:m61 pip show flask
WARNING: Package(s) not found: flask
```

Fix theano test (Kaggle#941)

http://b/178107003

Fix theano test (Kaggle#941)

http://b/178107003