query_engine crashes when querying SessionSeriesTable only with session_class_id or sample_count.
query_engine crashes when querying SessionSeriesTable
only with session_class_id or sample_count.

session_class_id and sample_count are not supposed
to be queried alone, there has to be some other field in
select with it. Return EINVAL if these fields are queried
alone.

Change-Id: I24574662b56b2ea26311983bc1e37c20d7f518f1
Closes-bug: #1731177

rombie/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller,eonpatapon/contrail-controller,eonpatapon/contrail-controller,eonpatapon/contrail-controller,eonpatapon/contrail-controller,eonpatapon/contrail-controller