RTSP Camera Agent: fix docker dependency and make copy for latest file

[davidvng]

Description

• Added opencv-python-headless dependency to Dockerfile
• Make a copy of latest file instead of creating symlink

Motivation and Context

• opencv-python only works for local installations, need headless version for Docker
• Symlinks not valid outside of docker container

How Has This Been Tested?

Tested on daq-dev

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[BrianJKoopman]

Looks good, some thoughts on possible configs that wouldn't require changes to the symlink section below.

[BrianJKoopman]

Thanks for the updates!