[jdk11u-dev] RFR: 8294402: Add diagnostic logging to VMProps.checkDockerSupport

[Amos Shi]

Backport of [JDK-8294402](https://bugs.openjdk.org/browse/JDK-8294402)

Unclean Backport:
- `test/jtreg-ext/requires/VMProps.java`
  - The `Copyright year` line are conflicting. Manually merged.
  - `log("Entering dockerSupport()")` base line are different. Manually merged.
  - This file can be considered as `Clean backport`

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Commit messages:
 - Backport 03d613bbab99dd84dfc5115a5034c60f4e510259

Changes: https://git.openjdk.org/jdk11u-dev/pull/2390/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2390&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8294402
  Stats: 88 lines in 1 file changed: 87 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2390.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2390/head:pull/2390

PR: https://git.openjdk.org/jdk11u-dev/pull/2390