Slows down block maintenance iteration (#543)

* Slows down block maintenance iteration

* Fixes unstable integration test.

codex/stores/maintenance.nim

@@ -78,6 +78,7 @@ proc runBlockCheck(self: BlockMaintainer): Future[void] {.async.} =
     if be =? await maybeBeFuture:
       inc numberReceived
       await self.processBlockExpiration(be)
+      await sleepAsync(50.millis)
 
   # If we received fewer blockExpirations from the iterator than we asked for,
   # We're at the end of the dataset and should start from 0 next time.

tests/integration/testblockexpiration.nim

@@ -65,7 +65,7 @@ ethersuite "Node block expiration tests":
 
     let contentId = uploadTestFile()
 
-    await sleepAsync(2.seconds)
+    await sleepAsync(3.seconds)
 
     expect TimeoutError:
       discard downloadTestFile(contentId)