RFR: 8260: Warnings and errors logged during XML processing

[Virag Purnam]

We have several xml files in JMC. To remove fortify scan issue about XML Validation, **DocumentBuilderFactory.setValidating(true)** had been added. Because of that validation was triggered during the parsing of XML. We do not have **xsd files** against all the xml files and so it shows errors and warning.  
We can either create **xsd files** or **disable the ErrorValidator**. 
I think at this point disabling the default ErrorValidator is better option, and I have done the same in this PR. 
Could you please review the changes. Thanks.

-------------

Commit messages:
 - 8260: Warnings and errors logged during XML processing

Changes: https://git.openjdk.org/jmc/pull/592/files
  Webrev: https://webrevs.openjdk.org/?repo=jmc&pr=592&range=00
  Issue: https://bugs.openjdk.org/browse/JMC-8260
  Stats: 9 lines in 5 files changed: 7 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jmc/pull/592.diff
  Fetch: git fetch https://git.openjdk.org/jmc.git pull/592/head:pull/592

PR: https://git.openjdk.org/jmc/pull/592