RFR: 8334332: TestIOException.java fails if run by root [v3]

[SendaoYan]

> Hi all,
>   Test `test/langtools/jdk/javadoc/doclet/testIOException/TestIOException.java` run fails with root user privileged. I think it's necessary to skip this testcase when user is root.
>   Why run the jtreg test by root user? It's because during rpmbuild process for linux distribution of JDK, root user is the default user to build the openjdk, also is the default user to run the `make test-tier1`, this PR make this testcase more robustness.
>   The change has been verified, only change the testcase, no risk.

SendaoYan has updated the pull request incrementally with one additional commit since the last revision:

  throw error()  ->  throw skip()

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/19731/files
  - new: https://git.openjdk.org/jdk/pull/19731/files/30916158..a9a770f2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19731&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19731&range=01-02

  Stats: 44 lines in 1 file changed: 1 ins; 29 del; 14 mod
  Patch: https://git.openjdk.org/jdk/pull/19731.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19731/head:pull/19731

PR: https://git.openjdk.org/jdk/pull/19731