selftest: Run smb2.compound_find against filesrever only, not nt4_dc and ad_dc

selftest: Run smb2.compound_find against filesrever only, not nt4_dc and ad_dc

This is a slow test of SMB2 protocol features, it needs not to be repeated.  It only
got run against both by accident at the original merge and then extended to
run on the [compount_find] share (with smbd:find async delay usec = 10000)
but really does not need to be run three times.

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>