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### _Why are the changes needed?_
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Follow up [KYUUBI #1002] [KYUUBI #1035] [KYUUBI #1037]
- correct the config key; we should use `spark.` as the prefix
- change the config to false by default
- correct the class loader; thread context is not safe, spark and hive often change it
- update the log and exception
following is the failed error msg:
```
Caused by: java.io.FileNotFoundException: file:/Users/cathy/Desktop/tmp/spark-3.1.2-bin-hadoop2.7/jars/kyuubi-extension-spark-3-1_2.12-1.4.0-SNAPSHOT.jar!/sql-classification-default.json (No such file or directory)
at java.io.FileInputStream.open0(Native Method)
at java.io.FileInputStream.open(FileInputStream.java:195)
at java.io.FileInputStream.<init>(FileInputStream.java:138)
at com.fasterxml.jackson.core.JsonFactory.createParser(JsonFactory.java:916)
at com.fasterxml.jackson.databind.ObjectMapper.readTree(ObjectMapper.java:2745)
at org.apache.kyuubi.sql.sqlclassification.KyuubiGetSqlClassification$.<init>(KyuubiGetSqlClassification.scala:51)
at org.apache.kyuubi.sql.sqlclassification.KyuubiGetSqlClassification$.<clinit>(KyuubiGetSqlClassification.scala)
... 59 more
```
### _How was this patch tested?_
- [ ] Add some test cases that check the changes thoroughly including negative and positive cases if possible
- [ ] Add screenshots for manual tests if appropriate
- [x] [Run test](https://kyuubi.readthedocs.io/en/latest/develop_tools/testing.html#running-tests) locally before make a pull request
Closes#1140 from ulysses-you/refine.
Closes#1002
f39ef2cf [ulysses-you] address comment
5cb94459 [ulysses-you] nit
de9fd932 [ulysses-you] test
78e8c147 [ulysses-you] default
6f23c63e [ulysses-you] refine
Authored-by: ulysses-you <ulyssesyou18@gmail.com>
Signed-off-by: Cheng Pan <chengpan@apache.org>
7a3545e748