RFR: 8291991: Adjust the "shared class paths mismatch" message if class path logging is enabled

[Calvin Cheung]

Before this fix, with `-Xshare:on` and `-Xlog:class+path=info` and if there is a class path mismatch, the following error message will be displayed:

`shared class paths mismatch (hint: enable -Xlog:class+path=info to diagnose the failure)`

After this fix, only the first part of the error message will be displayed since the "hint" is repetitive if the user has specified `-Xlog:class+path=info.`

`shared class paths mismatch`

Passed tiers 1 and 2 testing.

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Commit messages:
 - 8291991: Adjust the "shared class paths mismatch" message if class path logging is enabled

Changes: https://git.openjdk.org/jdk/pull/11078/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11078&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8291991
  Stats: 41 lines in 3 files changed: 32 ins; 0 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/11078.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11078/head:pull/11078

PR: https://git.openjdk.org/jdk/pull/11078