Updated Dockerfile and prebuild.sh to conform with guidance.

Twistlock Console v19_11_506 Followed the guidance outlined https://dccscr.dsop.io/dsop/dccscr/blob/master/contributor-onboarding/scripts/prebuild.sh and https://dccscr.dsop.io/dsop/dccscr/tree/master/contributor-onboarding#dccscrdcar-approved-container-requirements

Once this process works I will submit the Twistlock Defender