RFR: 8304172: ProblemList serviceability/sa/UniqueVtableTest.java

[Daniel D. Daugherty]

Trivial fixes to ProblemList a couple of tests:

[JDK-8304172](https://bugs.openjdk.org/browse/JDK-8304172) ProblemList serviceability/sa/UniqueVtableTest.java
[JDK-8304175](https://bugs.openjdk.org/browse/JDK-8304175) ProblemList compiler/vectorapi/VectorLogicalOpIdentityTest.java on 2 platforms

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Commit messages:
 - 8304175: ProblemList compiler/vectorapi/VectorLogicalOpIdentityTest.java on 2 platforms
 - 8304172: ProblemList serviceability/sa/UniqueVtableTest.java

Changes: https://git.openjdk.org/jdk/pull/13029/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13029&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8304172
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13029.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/13029/head:pull/13029

PR: https://git.openjdk.org/jdk/pull/13029