RFR: 8263897: compiler/c2/aarch64/TestVolatilesSerial.java failed with "java.lang.RuntimeException: Wrong method"

[Vladimir Kozlov]

The test assumes that testInt() method's compilation information will be first in output. 
But these tests did not run with -Xbatch or -XX:CICompilerCount=1 flag. They only use `-XX:-TieredCompilation` which does not guarantee which method is compiled first.

Added `-XX:-BackgroundCompilation` flag to make sure all test methods compiled in expected order.

Tested tier1-3 and 50x test run.

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Commit messages:
 - 8263897: compiler/c2/aarch64/TestVolatilesSerial.java failed with "java.lang.RuntimeException: Wrong method"

Changes: https://git.openjdk.java.net/jdk/pull/3103/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3103&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263897
  Stats: 12 lines in 1 file changed: 2 ins; 0 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3103.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3103/head:pull/3103

PR: https://git.openjdk.java.net/jdk/pull/3103