This commit fixes an old flake in the neutrino anchor output tests. It
turns out that sometimes with Neutrino we don't have enough UTXOs in our
wallet to sweep both the local and remote anchor. This is very likely a
timing issue, we need to give the wallet more time to catch up with the
chain and process all transactions to find unspent outputs.
We address this two-fold: We add an additional UTXO to Alice. And then
we also make sure we detect both UTXOs properly after restarting.
This commit refactors the function assertNumConnections to use
wait.NoError. Prior to this commit, `make lint` will fail on this
function. While fixing it, it's noticed that wait.NoError suits the
case so it's refactored to use it.
