tools: replace add with xadd (#3518)

resolve #3481
replace add with xadd for more tools.
diff --git a/tools/cachestat.py b/tools/cachestat.py
index bb94949..2c09d14 100755
--- a/tools/cachestat.py
+++ b/tools/cachestat.py
@@ -81,7 +81,7 @@
     u64 ip;
 
     key.ip = PT_REGS_IP(ctx);
-    counts.increment(key); // update counter
+    counts.atomic_increment(key); // update counter
     return 0;
 }