webengine: Mark tests insignificant

linux-g++-32_developer-build_Ubuntu_10.04_x86
linux-g++_bin-pkg-config_Ubuntu_11.10_x86
linux-g++_developer-build_qtnamespace_qtlibinfix_Ubuntu_11.10_x64
linux-g++_shadow-build_Ubuntu_11.10_x86

Change-Id: Ie9ced8d28af62c464ef592ee4c05513b1bbf5558
Reviewed-by: Simo Fält <simo.falt@theqtcompany.com>