[lworld] RFR: 8281281: [lworld] Preload attribute code needs some fixes

[Frederic Parain]

Please review those small fixes in the Preload attribute code.

Thank you,

Fred

-------------

Commit messages:
 - Various fixes in Preload attribute support

Changes: https://git.openjdk.java.net/valhalla/pull/626/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=626&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8281281
  Stats: 58 lines in 5 files changed: 50 ins; 4 del; 4 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/626.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/626/head:pull/626

PR: https://git.openjdk.java.net/valhalla/pull/626