RFR: 8314501: Shenandoah: sun/tools/jhsdb/heapconfig/JMapHeapConfigTest.java fails

[Aleksey Shipilev]

Current test expects `G1HeapRegionSize` flag to be printed out from jmap. But that one is not printed when Shenandoah is enabled. I opted for the minimally intrusive fix: move the additional Shenandoah printout to the Shenandoah-specific block.

Additional testing:
 - [x] Affected test now passes with Shenandoah, continues to pass with G1, Serial, Parallel
 - [x] `sun/tools/jhsdb` passes with {Serial, Parallel, G1, Shenandoah}
 - [x] `serviceability/sa` passes with {Serial, Parallel, G1, Shenandoah}

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jdk/pull/15328/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15328&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8314501
  Stats: 6 lines in 1 file changed: 1 ins; 4 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15328.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15328/head:pull/15328

PR: https://git.openjdk.org/jdk/pull/15328