Rewrite odcs-manager to not use flask-script
    
    Rewrite using flask command line interface as flask-script is deprecated
    for a long time and this means flask >= 0.11 is required (RHEL7 only
    provides python-flask-0.10).
    
    Refer to https://flask.palletsprojects.com/en/0.12.x/cli/
    
    FIXES: https://pagure.io/odcs/issue/504
    JIRA: RHELCMP-126
    Signed-off-by: Haibo Lin <hlin@redhat.com>