RFR: 8275689: [TESTBUG] Use color tolerance only for XRender in BlitRotateClippedArea test

[Jayathirth D V]

This is follow up change after : https://bugs.openjdk.java.net/browse/JDK-8255724

Now color tolerance is only added for Linux(XRender is default pipeline in Linux and Solaris is not supported anymore). So I am using jdk.test.lib.Platform to determine which OS we are running on. CI run on all platforms is green.

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Commit messages:
 - 8275689: [TESTBUG] Use color tolerance only for XRender in BlitRotateClippedArea test

Changes: https://git.openjdk.java.net/jdk/pull/6119/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6119&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8275689
  Stats: 30 lines in 1 file changed: 19 ins; 0 del; 11 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6119.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6119/head:pull/6119

PR: https://git.openjdk.java.net/jdk/pull/6119