Disable access to the field keyword in the new SQL engine.

[penghuo]

In the legacy engine, the following query is workable

SELECT firstname.keyword FROM

In the new engine, we the query will throw Semantic Exception because

1. Customer should not aware of the keyword, the query engine should expanded it automatically.
2. firstname.keyword is not the valid field in the symbol table/mapping. In DSL, firstname.keyword can't be used directly when select fields. {"from":0,"size":200,"timeout":"1m","_source":{"includes":["firstname.keyword"],"excludes":[]}}