RFR(S) : 8238049 : TieredCompilation shouldn't be re-enabled if CompilationMode is high-only

[Igor Ignatyev]

http://cr.openjdk.java.net/~iignatyev/8238049/webrev.00/
> 9 lines changed: 3 ins; 2 del; 4 mod;


Hi all,

could you please review the small and trivial-ish patch?
from JBS:
> currently, if you run java w/ -XX:-TieredCompilation -XX:+UseJVMCICompiler, TieredCompilation will be set back to true and change CompilationMode from "default" to "high-only-quick-internal" (w/o actually changing the value of the flag though). if you run it w/ '-XX:-TieredCompilation -XX:+UseJVMCICompile -XX:CompilationMode=high-only', TieredCompilation will be changed to true, but CompilationMode will remain high-only, so effectively it just needlessly enables TieredCompilation.

the patch not only leaves TieredCompilation disabled when CompilationMode is high-only, but also changes the actual value of CompilationMode flag, so it will be properly reported.

JBS: https://bugs.openjdk.java.net/browse/JDK-8238049
webrev: http://cr.openjdk.java.net/~iignatyev/8238049/webrev.00/
testing: manual by java -XX:+PrintFlagsFinal w/ {-TieredCompilation,+TieredCompilation}x{CompilationMode=default,CompilationMode=high-only,""}

Thanks,
-- Igor