build: checkout *.po files at the end of makerpms.sh
    
    *.po are re-generated during build. These changes shouldn't be
    comitted to git unless translation have been updated (during
    release).
    
    Fixes https://pagure.io/freeipa/issue/6605
    
    Signed-off-by: Tomas Krizek <tkrizek@redhat.com>
    Reviewed-By: Pavel Vomacka <pvomacka@redhat.com>