[autotests] tst_QTreeView::styleOptionViewItem test unstable

tst_QTreeView::styleOptionViewItem test is unstable on the Ubuntu 11.10 x64 platform.

PASS (with WARNING) - http://testresults.qt-project.org/ci/QtBase_master_Integration/build_01526/linux-g++_developer-build_qtnamespace_qtlibinfix_Ubuntu_11.10_x64/log.txt.gz
FAIL - http://testresults.qt-project.org/ci/QtBase_master_Integration/build_01527/linux-g++_developer-build_qtnamespace_qtlibinfix_Ubuntu_11.10_x64/log.txt.gz
PASS (with WARNING) - http://testresults.qt-project.org/ci/QtBase_master_Integration/build_01531/linux-g++_developer-build_qtnamespace_qtlibinfix_Ubuntu_11.10_x64/log.txt.gz
FAIL - http://testresults.qt-project.org/ci/QtBase_master_Integration/build_01535/linux-g++_developer-build_qtnamespace_qtlibinfix_Ubuntu_11.10_x64/log.txt.gz

I have only seen failures since build 01544 (to 01554), however this still looks like a unstable failure.