test: remove CONFIG+=insignificant_test for tst_qgraphicstransform

test: remove CONFIG+=insignificant_test for tst_qgraphicstransform

This autotest failure is stable, so it should be marked with
QEXPECT_FAIL, not CONFIG+=insignificant_test.

Note that the test row naming had to be changed, as the test previously
created many rows of testdata with the same name, making it impossible
to skip only the broken rows.

Task-number: QTBUG-20661
Change-Id: Ie38f5dddafe7686e30eaa8ff3445310935d2cd9a
Reviewed-on: http://codereview.qt.nokia.com/2419
Reviewed-by: Sergio Ahumada <sergio.ahumada@nokia.com>
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>