web-client: sending the same tx twice takes too much time

[Albermonte]

Context:

In Nimiq Pay, we send the transaction from the cosigning server and from the app itself. We do this because cosigning is faster and we don't depend on the network connection speed of the app. But as it is possible that by some chance it might fail, we also send the same tx from the app to make sure that it has always been sent.
This leads to the app taking always more than 10 seconds to send the tx.

Causes:

• Subscribing for addresses takes 2-3 seconds or more
• Sending the tx doesn't check if it is already included and that causes that waiting for the transaction will always timeout

As you can see in this Nimiq Playground the first tx is sent within 2 to ~10 seconds and the second one always takes >10 seconds

Consensus: established

Sender: NQ89 8KKB BSKT 6BNC JTH6 1ECS TC7C CM0Y B87V
Recipient: NQ62 P0QP M050 CY0L LS6V U8YK K59G RP6R HAE3

First tx took: 2151ms
Second tx took: 12071ms