Makes Docker directly handle the SIGINT signal

[jbaptperez]

Description

Caldera needs the SIGINT signal to be properly stopped.
As Docker defaults to the SIGTERM signal, a workaround was, until now, to manually send the SIGINT signal.

This PR makes the Docker image directly set the signal tu use when stopping a related container.

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Building a new image and invoking docker stop <container-id> instead of docker kill --signal=SIGINT <container-id>.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works

[elegantmoose]

@clenk Im fine with this. Thoughts?

[clenk]

LGTM