Add support for new --isolated and --koji-parent-build arguments to the container-build sub-command.

For --isolated: Isolated builds will only update the "{version}-{release}" unique tag and the primary tag in target container registry. Also, OSBS's bump_release plugin will ignore isolated builds. Users must specify a --build-release argument when the use the --isolated argument.

For --koji-parent-build: OSBS allows users to dynamically override the Dockerfile's "FROM" image at build time. This allows you to build your container against a specific parent image without pushing changes to dist-git.