When a casueword32 operation fails, 'do_sem2_wake' will call
'thread_check_susp' to avoid a potential livelock. However, it
instructs 'thread_check_susp' to sleep while holding a previously busied
umtxq key. This is explicitly discouraged by the comments in
'thread_check_susp' which state that a thread shouldn't sleep if it
owns a kernel resource. Fix this by passing 'false'
to 'thread_check_susp'.
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