RFR: 8316892: Skip failing IconifyTestcanIconifyDecoratedStage on Linux

[Lukasz Kostyra]

Failing test is skipped. Verified on Ubuntu VM.

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Commit messages:
 - Skip canIconifyDecorated test

Changes: https://git.openjdk.org/jfx/pull/1250/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1250&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316892
  Stats: 3 lines in 1 file changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/1250.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1250/head:pull/1250

PR: https://git.openjdk.org/jfx/pull/1250