MXS-1406 Report CALL operation

Basically it would be trivial to report far more operations
explicitly, but for the fact that the values in qc_query_op_t
currently, quite unnecessarily, form a bitmask.

In 2.2 that is no longer the case, so other operations will be
added there.

query_classifier/test/maxscale.test

@@ -83,4 +83,7 @@ SELECT her FROM (SELECT @@server_id as her) as t WHERE her REGEXP '.*';
 select * from db1.t1 union select * from db2.t2;
 
 # Names is a keyword as well
-select names from t;
+select names from t;
+
+call p1();
+call p1(@var);