RFR: 8278131: runtime/cds/appcds/dynamicArchive/* tests failing in loom repo

[Calvin Cheung]

A few dynamic archive CDS tests are failing in the loom repo due to more aggressive GC of code cache
which leads to unloading of some classes before being written into a dynamic CDS archive.

This change is to make the affected tests more reliable by ensuring the test classes are not unloaded
during dynamic CDS dump time.

Testing: Oracle CI tiers 1,2,4.

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Commit messages:
 - fix trailing whitespace
 - 8278131: runtime/cds/appcds/dynamicArchive/* tests failing in loom repo

Changes: https://git.openjdk.java.net/jdk/pull/6843/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6843&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8278131
  Stats: 57 lines in 9 files changed: 45 ins; 0 del; 12 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6843.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6843/head:pull/6843

PR: https://git.openjdk.java.net/jdk/pull/6843