Adds docker pull tests and some changes in docker test call structure + some fix

Adds possibility for start subsubtest directly from cmd line.
   docker: Allows choose subsubtests to run
merge subsubtest config values with subtest config values and pass them to subsubtest
        It saves lots of duplicated lines.
    docker: Docker subsubtest config is merged with parent config
adds return value to remote_image_*
    docker: image adds return status to remove_image_* commands.
adds docker pull tests
    docker: Adds subtests for pull command.