tapgarden: pre proof retrieval delay respects context done signal

tapgarden/custodian.go

@@ -388,7 +388,14 @@ func (c *Custodian) inspectWalletTx(walletTx *lndclient.Transaction) error {
 
 			// Sleep to give the sender an opportunity to transfer
 			// the proof to the proof courier service.
-			time.Sleep(defaultProofRetrievalDelay)
+			// Without this delay our first attempt at retrieving
+			// the proof will very likely fail. We should expect
+			// retrieval success before this delay.
+			select {
+			case <-time.After(defaultProofRetrievalDelay):
+			case <-ctx.Done():
+				return
+			}
 
 			// Attempt to receive proof via proof courier service.
 			loc := proof.Locator{