ipaplatform/debian: fix path to ldap.so
    
    bind-dyndb-ldap on Debian installs ldap.so in a subdirectory of
    /usr/lib to prevent unintentional usage of an unversioned .so.
    The default settings for FreeIPA on Debian used an incomplete
    path, resulting in a failure to find ldap.so when bind attempts to
    start with bind-dyndb-ldap configured.
    
    This fixes the default path to use the appropriate location in its
    multiarch-qualified path.
    
    Signed-off-by: Jarl Gullberg <jarl.gullberg@gmail.com>
    Reviewed-By: Timo Aaltonen <tjaalton@ubuntu.com>