MXS-2713 Classify SET PASSWORD as QUERY_TYPE_WRITE

A change of the password is replicated to the slaves, so it
must only be sent to the master.

query_classifier/test/maxscale.test

@@ -136,3 +136,6 @@ SET @saved_cs_client= @@character_set_client;
 # MXS-2699
 SELECT NEXTVAL(id_generator), context FROM t1 WHERE (a,b,c) >= (1,2,3);
 select soundex(_utf8mb4 0xD091D092D093) as vx, gray_user_tag from user_extends where user_id > last_insert_id();
+
+# MXS-2713
+SET PASSWORD FOR 'user'@'10.0.0.1'='*C50EB75D7CB4C76B5264218B92BC69E6815B057A';