[jdk11u-dev] RFR: 8223138: Small clean-up in loop-tree support.

[Goetz Lindenmaier]

I downport this for parity with 11.0.13-oracle.

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Commit messages:
 - Backport 205085d8d5143c0d8517bcfc021457492a329c18

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/445/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=445&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8223138
  Stats: 28 lines in 3 files changed: 2 ins; 10 del; 16 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/445.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/445/head:pull/445

PR: https://git.openjdk.java.net/jdk11u-dev/pull/445