Use pungi_buildinstall without NFS
    
    The plugin supports two modes of operation:
    1. Mount a shared storage volume into the runroot and have the output
       written there.
    2. Have the plugin create a tar.gz with the outputs and upload them to
       the hub, from where they can be downloaded.
    
    This patch switches from option 1 to option 2.
    
    This requires all input repositories to be passes in as URLs and not
    paths. Once the task finishes, Pungi will download the output archives
    and unpack them into the expected locations.
    
    JIRA: RHELCMP-13284
    Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>