RFR: 8279573: compiler/codecache/CodeCacheFullCountTest.java fails with "RuntimeException: the value of full_count is wrong." [v2]

[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.

Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:

  I misunderstood the UseCodeCacheFlushing flag and make it act like MethodFlushing, which is a whole different flag.  Using MethodFlushing instead in the test makes it pass on loom and mainline.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7629/files
  - new: https://git.openjdk.java.net/jdk/pull/7629/files/7b790e07..03950bf0

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7629&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7629&range=00-01

  Stats: 6 lines in 2 files changed: 0 ins; 2 del; 4 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