RFR: 8279573: compiler/codecache/CodeCacheFullCountTest.java fails with "RuntimeException: the value of full_count is wrong."

[Coleen Phillimore]

This change adds a conditional to make -XX:-UseCodeCacheFlushing not flush the code cache so that the test passes on loom.  It also makes full_count atomic so that the test in codeCache for printing is correct.  This change also fixes the test because the full_count field and the message printing are not synchronized, so you can get 2 or more depending on the number of compiler threads.
Tested with tier1-3 on linux and windows x64.

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Commit messages:
 - 8279573: compiler/codecache/CodeCacheFullCountTest.java fails with "RuntimeException: the value of full_count is wrong."

Changes: https://git.openjdk.java.net/jdk/pull/7629/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7629&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279573
  Stats: 12 lines in 4 files changed: 3 ins; 0 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7629.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7629/head:pull/7629

PR: https://git.openjdk.java.net/jdk/pull/7629