RFR: 8278158: jwebserver should set request timeout

[Julia Boes]

This change sets a maximum request time for the `jwebserver` (and `java -m jdk.httpserver`), unless it has already been set. 

While here, I removed a comment from the implementation classes, a left-over from the pre-module era that is not needed and should not have been included in the first place.

Testing: tier 1-3, and manual testing to confirm a request fails after the given time, e.g.:

$ curl https://127.0.0.1:8000
curl: (35) LibreSSL SSL_connect: SSL_ERROR_SYSCALL in connection to 127.0.0.1:8000

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Commit messages:
 - initial commit

Changes: https://git.openjdk.java.net/jdk/pull/6737/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6737&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8278158
  Stats: 42 lines in 2 files changed: 32 ins; 10 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6737.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6737/head:pull/6737

PR: https://git.openjdk.java.net/jdk/pull/6737