RFR: 8288651: CDS test HelloUnload.java should not use literal string as ClassLoader name

[Calvin Cheung]

A simple test fix for changing the class loader name to a non-literal string so that the symbol refcount could be decremented upon unloading of the class loader.

Passed tiers 1 and 2 testing. Inspected the .jtr file to check the symbol refcount was decremented.

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Commit messages:
 - 8288651: CDS test HelloUnload.java should not use literal string as ClassLoader name

Changes: https://git.openjdk.org/jdk/pull/9297/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9297&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8288651
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/9297.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9297/head:pull/9297

PR: https://git.openjdk.org/jdk/pull/9297