idempotent KojiBuilder implementation of rida/builder.py
    
    * allows to call build() and connect() multiple times
      This needs to be followed by allowing resubmiting module build tasks in REST
    * rename buildroot_add_repo to buildroot_add_repos() (input data is artifactS)
    * Nils is disappointed by Guido
    
    Signed-off-by: Lubos Kocman <lkocman@redhat.com>