Do not skip symlinks when searching for old compose.
    
    ODCS creates symlinks to real directories containing the composes.
    The directory structure is similar to following one:
    
    - `./nightly/Fedora-Rawhide-20200304.n.0` -> `../odcs-3`
    - `./nightly/Fedora-Rawhide-20200305.n.0` -> `../odcs-4`
    - `./nightly/latest-Fedora-Rawhide` -> `../odcs-5`
    
    The current Pungi code to search for old composes skips symlinks
    and therefore old ODCS composes are not found.
    
    This commit removes this check and therefore symlinks are allowed
    when searching for old compose.
    
    I think this check existed to prevent using `latest-*` symlink as
    source for the compose. But this is not possible, because the
    code checks that the old compose directory name has certain pattern
    constructed from release_short, release_version, ... The `latest-*`
    symlink definitely does not match this pattern.
    
    I also executed test compose and it worked as expected.
    
    Signed-off-by: Jan Kaluza <jkaluza@redhat.com>