ldap_child: fix coverity warning
    
    In ldap_child_get_tgt_sync() variable 'ret' got overriden in done
    section without ever before being read.
    
    Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>
    (cherry picked from commit 6ccda8691123bb27f5f2a88a0c80174af3e0fd0a)