closureiters: fixes #15243 (#15454) [backport:1.2]

* fixes #15243 [backport:1.2]

(cherry picked from commit aa1d7fe1e9)

tests/async/tbreak_must_exec_finally.nim

@@ -0,0 +1,25 @@
+discard """
+  output: '''
+finally handler 8
+do not duplicate this one
+'''
+"""
+
+# bug #15243
+
+import asyncdispatch
+
+proc f() {.async.} =
+  try:
+    while true:
+      try:
+        await sleepAsync(400)
+        break
+      finally:
+        var localHere = 8
+        echo "finally handler ", localHere
+  finally:
+    echo "do not duplicate this one"
+
+when isMainModule:
+  waitFor f()