fix: TEC-1680/more-fixes2

[McSim85]

This PR

1. removes entrypoint.sh.
   Drone CI overrides entrypoint.sh if the pipeline has commands: defined.
   (c) https://docs.drone.io/pipeline/docker/syntax/steps/
   which says

The commands are executed inside the root directory of your git repository. The root of your git repository, also called the workspace, is shared by all steps in your pipeline. This allows file artifacts to persist between steps. NB “commands” overrides the docker entrypoint.

2. modifies ANSIBLE_STRATEGY_PLUGINS
   Because we cannot use entrypoint with Drone, the only way to define ANSIBLE_STRATEGY_PLUGINS is to hardcode the path into Dockerfile and also, I have added an if statement, that will verify if path changed or not during the build process.

3. Adds final apt-get update
   We need apt-get update for backward compatibility with Drone CI tasks that run apt-get install X without apt-get update.