Removed a parameter from handleAttrWithMessage to make it more consistent with other attribute handlers, as well as other attribute error messages.  Added missing test cases for the unavailable attribute, and updated the deprecated test case.
tsan: treat SIGSYS as synchronous signal
It is required for chromium sandboxing code.
From the description it seems to be indeed synchronous -- called back on syscall with incorrect arguments,
but seems to be unused in practice. So this should be fine.