tsan: relax check for errno spoiling more

We do not detect errno spoiling for SIGTERM,
because some SIGTERM handlers do spoil errno but reraise SIGTERM,
tsan reports false positive in such case.
It's difficult to properly detect this situation (reraise),
because in async signal processing case (when handler is called directly
from rtl_generic_sighandler) we have not yet received the reraised
signal; and it looks too fragile to intercept all ways to reraise a signal.

llvm-svn: 200742