Review and fix some usages of Future.cancel; Bump Chronos

Author: zah

beacon_chain/eth1_monitor.nim

@@ -404,7 +404,7 @@ proc init*(T: type Eth1Monitor,
   let web3Fut = newWeb3(web3Url)
   yield web3Fut or sleepAsync(chronos.seconds(5))
   if (not web3Fut.finished) or web3Fut.failed:
-    web3Fut.cancel()
+    await cancelAndWait(web3Fut)
     return err "Failed to setup web3 connection"
 
   let

beacon_chain/eth2_network.nim

@@ -789,13 +789,10 @@ proc dialPeer*(node: Eth2Node, peerAddr: PeerAddr, index = 0) {.async.} =
         deadline.cancel()
       inc nbc_successful_dials
     else:
-      # TODO(cheatfate): As soon as `nim-libp2p` will be able to handle cancellation
-      # properly and will have cancellation tests, we need add here cancellation
-      # of `workfut`.
-      # workfut.cancel()
       debug "Connection to remote peer timed out"
       inc nbc_timeout_dials
       node.addSeen(peerAddr.peerId, SeenTableTimeTimeout)
+      await cancelAndWait(workfut)
   except CatchableError as exc:
     debug "Connection to remote peer failed", msg = exc.msg
     inc nbc_failed_dials