Relaxed an assert statement: a thread canceled by pthread_cancel() can really exit with synchr_nesting > 0.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@9151 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/drd/drd_thread.c b/drd/drd_thread.c
index b57140f..af137c5 100644
--- a/drd/drd_thread.c
+++ b/drd/drd_thread.c
@@ -282,7 +282,7 @@
 
   tl_assert(0 <= (int)tid && tid < DRD_N_THREADS
             && tid != DRD_INVALID_THREADID);
-  tl_assert(s_threadinfo[tid].synchr_nesting == 0);
+  tl_assert(s_threadinfo[tid].synchr_nesting >= 0);
   for (sg = s_threadinfo[tid].last; sg; sg = sg_prev)
   {
     sg_prev = sg->prev;