RFR: 8273376: Zero: Disable vtable/itableStub gtests

[Aleksey Shipilev]

Simple test bug fix.

Additional testing:
 - [x] Linux x86_64 Server still runs the test
 - [x] Linux x86_64 Zero now skips the test

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Commit messages:
 - Fix

Changes: https://git.openjdk.java.net/jdk/pull/5377/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5377&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273376
  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5377.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5377/head:pull/5377

PR: https://git.openjdk.java.net/jdk/pull/5377