Use BASE_IMAGE in final stage FROM and misc fixes

• Set BASE_IMAGE build arg and use

  FROM ${BASE_REGISTRY:-}${BASE_REGISTRY:+/}${BASE_IMAGE}:${BASE_TAG}

  for final stage to comply with DSOP hardening requirements

• Replace hard-coded Redhat registry reference in gitlab-base Dockerfile.

• Do not set FIPS_MODE=1 We need to use fips images to enable FIPS mode, not the current stock UBI images. Unset for now.