[SSSD] [PATCH] memberof: Do not create request with 0 attribute values

[Lukas Slebodnik]

ehlo,

at first I thought it is related to ticket "#2576"
but after simplification of reproducer I found out it just looks
bad in log file.

ldb failed to add attribute with 0 values to ldb entry, but it would not have
any effect.

BTW The best would be to immediately skip request. I'm not sure how to do it
with plain ldb.

How to reproduce?
* import attached ldif
* getent group "Escalation"
* sss_cache -E
* getent group "Escalation"

BTW you can see more warnings if nested hierarchy is deeper and each
group directly contains the same user.

LS