Remove duplicate '-t' CLI flag
Allow setting different dockerfile name (#52) Patchman team uses different Dockerfile name i.e. https://github.com/RedHatInsights/patchman-engine/blob/master/Dockerfile.rhel8
Allow setting different dockerfile name (#52) Patchman team uses different Dockerfile name i.e. https://github.com/RedHatInsights/patchman-engine/blob/master/Dockerfile.rhel8