Build forked repo directly in Koji
    
    This change allows building changes pushed into the user's forked repo.
    This doesn't require using '--srpm' param, 'fedpkg (scratch-)build' is
    enough. Function restricts using multiple git remote records. Otherwise,
    the original approach works.
    
    JIRA: COMPOSE-2963
    Relates: #282
    
    Signed-off-by: Ondrej Nosek <onosek@redhat.com>