moon jieun

@tbonelee @pan3793 Thank you for mentioning the white space issue. I put the eliminating white spaces logic to block the unallowable configurations with white space included such as : `allow%20LoadLocalInfile=true`...

https://github.com/apache/zeppelin/pull/4882 (Java release to 11) is merged to master branch. Can @pan3793 review this pr, so I can merge this branch?

- changed the PR title to show the key change. - changed code to fail immediately if url decoding throws error. Previously, I thought if decoding step fails, validating logic...

Thanks for @Reamer, I fix the `URLDecoder.decode` method to fit for java 11. Additionally, in[ java 11 URLDecoder](https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/net/URLDecoder.html), it never throws [UnsupportedEncodingException](https://docs.oracle.com/javase/8/docs/api/java/io/UnsupportedEncodingException.html) so I removed the relevant try-catch statement.

@Reamer I rebased my pr after the master branch, and applied your reviews ([fix indent & remove unused import](https://github.com/apache/zeppelin/pull/4838/commits/b22eafe7fe56b806fe53e64b6a3ab374d803504a)). Please check for it!