[lworld] RFR: 8369044: [lworld] Interpreter does not emit barrier at the end of java.lang.Object::<init>

[Frederic Parain]

The rewriting of the _return bytecode in j.l.Object.<init> method was preventing the generation of the barrier, this fix solves the issue.

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Commit messages:
 - Fix init barrier for j.l.Object

Changes: https://git.openjdk.org/valhalla/pull/1652/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1652&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8369044
  Stats: 4 lines in 2 files changed: 2 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/valhalla/pull/1652.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1652/head:pull/1652

PR: https://git.openjdk.org/valhalla/pull/1652