selftest/knownfail.d: move labdc to expectedfail.d

To quote the original commit:

> Note that the rpc.echo tests for the testallowed and testdenied users
> fail, because we don't backup the secrets for these users. So these
> tests failing proves that the lab-DC testenv is correct.

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

diff --git a/selftest/knownfail.d/labdc b/selftest/expectedfail.d/labdc
similarity index 100%
rename from selftest/knownfail.d/labdc
rename to selftest/expectedfail.d/labdc