Reduce size of docker image for tpm20 tests
Reduce size of docker image for tpm20 tests

Some improvements to reduce the final size of the image:
Using a list of packages for dependencies
Aggregating some RUN commands
Initializing dnf cache
Removing dnf cache

Also removed duplicate ENV container docker entry

The total size save is around 300MB

mit-ll/python-keylime,mit-ll/python-keylime,mit-ll/python-keylime,mit-ll/python-keylime