[lworld] RFR: 8280704: [lworld] Rename defaultvalue to aconst_init in tests

[David Simms]

Renamed defaultvalue to aconst_init

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Commit messages:
 - Renamed defaultvalue to aconst_init

Changes: https://git.openjdk.java.net/valhalla/pull/618/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=618&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8280704
  Stats: 31 lines in 12 files changed: 0 ins; 0 del; 31 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/618.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/618/head:pull/618

PR: https://git.openjdk.java.net/valhalla/pull/618