[Scons/Test] Allow test suite to continue if gtest crashes

If a gtest program crashes, register that as a single test failure.
Previously, the entire test suite would be aborted because the
attempt to open the test results file (gtest-foo.xml) would fail.

git-svn-id: https://cantera.googlecode.com/svn/cantera/trunk@2777 02a645c2-efd0-11dd-984d-ab748d24aa7e