[code-reflection] Integrated: Regression: HAT tests broken after pull/677

[Maurizio Cimadamore]

The revised `MethodRef::resolveToMethod` fails to resolve non-static method due to a subtle bug in the combo lookup.

We should add more tests here, and possibly consolidate the lookup code,
but for now I'll just fix the regression and come back later (as this is impacting HAT work).

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Commit messages:
 - Fix issue in method resolution

Changes: https://git.openjdk.org/babylon/pull/680/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=680&range=00
  Stats: 7 lines in 2 files changed: 3 ins; 2 del; 2 mod
  Patch: https://git.openjdk.org/babylon/pull/680.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/680/head:pull/680

PR: https://git.openjdk.org/babylon/pull/680