On --disable-openssl, let's avoid linking the
bundled libxmlsec to OpenSSL by passing down
--without-openssl to its configure script.

Change-Id: I04447683adeba4b7059e94579adf43ef788a4916
Reviewed-on: https://gerrit.libreoffice.org/3329Reviewed-by: David Tardon <dtardon@redhat.com>
Tested-by: David Tardon <dtardon@redhat.com>