Workaround bar_bad testcase hanging with newer glibc in helgrind/drd tests.

Workaround bar_bad testcase hanging with newer glibc in helgrind/drd tests.

This is a workaround for bug #358213 helgrind/drd pthread_barrier tests
hangs with new glibc pthread barrier implementation. This makes sure that
the tests don't hang anymore. It does this by creating new threads that
sleep and kill the other threads after some time. But this introduces
some non-determinism that might cause the tests to occassionally fail
(both against old and new glibc implementations).

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@15962