RFR: 8243110: SVGTest.testSVGRenderingWithPattern fails intermittently

[Arun Joseph]

Issue: Snapshot taken before webpage is rendered

Fix: Use stateProperty and sleep to wait for the page to finish rendering

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Commit messages:
 - Add sleep
 - 8243110: SVGTest.testSVGRenderingWithPattern fails intermittently

Changes: https://git.openjdk.java.net/jfx/pull/240/files
 Webrev: https://webrevs.openjdk.java.net/jfx/240/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8243110
  Stats: 18 lines in 1 file changed: 15 ins; 2 del; 1 mod
  Patch: https://git.openjdk.java.net/jfx/pull/240.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/240/head:pull/240

PR: https://git.openjdk.java.net/jfx/pull/240