Run shellcheck and correct various things it noted.
    
    Review very welcome.
    
    Without this the pungi command is failing with:
    
    ./release-candidate.sh: line 98: pungi-koji --notification-script=/usr/bin/pungi-fedmsg-notification     --notification-script=pungi-wait-for-signed-ostree-handler     --config=fedora-beta.conf --old-composes=/mnt/koji/compose/41   --skip-phase=productimg     --label=Beta-1.1 --target-dir=/mnt/koji/compose/41: No such file or directory
    ========================================
    RUN THE COMPOSE. EXIT IF THE EXIT STATUS IS NOT ZERO.
    
    usage: pungi-koji [-h] (--target-dir PATH | --compose-dir PATH)
                      [--label LABEL] [--no-label] [--supported]
                      [--old-composes PATH] --config CONFIG [--skip-phase PHASE]
                      [--just-phase PHASE] [--nightly] [--test] [--ci]
                      [--production] [--development] [--koji-event ID] [--version]
                      [--notification-script NOTIFICATION_SCRIPT]
                      [--no-latest-link] [--latest-link-status STATUS]
                      [--latest-link-components LATEST_LINK_COMPONENTS]
                      [--parent-compose-id PARENT_COMPOSE_ID]
                      [--respin-of RESPIN_OF] [--print-output-dir] [--quiet]
    pungi-koji: error: one of the arguments --target-dir --compose-dir is required
    
    I think this should fix it, but more eyes welcome.
    
    Signed-off-by: Kevin Fenzi <kevin@scrye.com>