RFR: JDK-8290126: Add a check in JavadocTester for "javadoc should not crash" [v3]

[Jonathan Gibbons]

> Please review a simple update to `JavadocTester` to provide a default-on check that no stack traces were written to the STDERR stream.
> 
> There are also some minor cleanup edits suggested by the IDE.

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

  revert (defer) improvement of TagletManager error message; fix TestTFMBuilder.java

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Changes:
  - all: https://git.openjdk.org/jdk/pull/9458/files
  - new: https://git.openjdk.org/jdk/pull/9458/files/2a970211..9d4859f1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9458&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9458&range=01-02

  Stats: 4 lines in 3 files changed: 2 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/9458.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9458/head:pull/9458

PR: https://git.openjdk.org/jdk/pull/9458