added custom message in failure

[eruffaldi]

TestFailure/TestError should report the custom error text message as specified in the check.

Before Patch:

<testsuite name="TestSuite">
<testcase classname="test1case" name="testExample1" time="0.047057628631592">
  <failure message="Test Failure" type="testFailure">TEST_FAILURE: 3.000000 != 4.000000</failure>
</testcase>
</testsuite>

After Patch:

<testsuite name="TestSuite">
<testcase classname="test1case" name="testExample1" time="0.047057628631592">
  <failure message="MESSAGE" type="testFailure">TEST_FAILURE: 3.000000 != 4.000000</failure>
</testcase>
</testsuite>

Where MESSAGE is the one passed to the pass VI:

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