lnd_test: update testInvoiceRoutingHints to account
lnd_test: update testInvoiceRoutingHints to account

In this commit, we open an additional channel between Bob and Carol to
ensure that Bob gets selected as the only routing hint. Previously Bob
would get selected, but with the recent changes, it would no longer
happen due to him not having any advertised edges.

aakselrod/lnd,aakselrod/lnd,LightningNetwork/lnd,LightningNetwork/lnd