RFR: 8305937: com/sun/jdi/SetLocalWhileThreadInNative.java fails with -XX:+TieredCompilation

[Leonid Mesnik]

Could you please review following trivial fix which correct jvm options order in TestScaffold.
TestScaffold combines test optionos and jtreg vm options. Before [JDK-8304834](https://bugs.openjdk.org/browse/JDK-8304834) it passed test jvm args as part of targetAppCommandLine. So the test VM args are added to the jtreg vm options. But after JDK-8304834 it parse then into targetVMArgs. So test vm args should append to jtreg vm options to override them.

Testing: tier1-tier5 (including failing combination and testing with wrapper)
I haven't added requires to filter out the test, because e filter only failing combination usually.

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Commit messages:
 - 8305937: com/sun/jdi/SetLocalWhileThreadInNative.java fails with -XX:+TieredCompilation

Changes: https://git.openjdk.org/jdk/pull/13462/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13462&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305937
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13462.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13462/head:pull/13462

PR: https://git.openjdk.org/jdk/pull/13462