RFR: 8286967: Unproblemlist compiler/c2/irTests/TestSkeletonPredicates.java and add additional test for JDK-8286638

[Christian Hagedorn]

[JDK-8286361](https://bugs.openjdk.java.net/browse/JDK-8286361) could be traced back to the same underlying problem as in [JDK-8286638](https://bugs.openjdk.java.net/browse/JDK-8286638). Pulling in the change fixed the problem.

This patch unproblemlists the previously failing test and adds a new test for JDK-8286638 (extracted from compiler/c2/irTests/TestSkeletonPredicates.java) that I've used for analyzing JDK-8286361.

Testing with latest JDK:
- hs-tier1-4 flags for the new test
- hs-tier7+8 flags for compiler/c2/irTests/TestSkeletonPredicates.java

Thanks,
Christian

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Commit messages:
 - remove newline
 - 8286967: Unproblemlist compiler/c2/irTests/TestSkeletonPredicates.java and add additional test for JDK-8286638

Changes: https://git.openjdk.java.net/jdk/pull/8806/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8806&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8286967
  Stats: 79 lines in 2 files changed: 77 ins; 2 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8806.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8806/head:pull/8806

PR: https://git.openjdk.java.net/jdk/pull/8806