chainntnfs: increase timeout in unit tests

[yyforyongyu]

Fix the unit test flake we've seen recently,

--- FAIL: TestHistoricalConfDetailsTxIndex (0.00s)
    --- FAIL: TestHistoricalConfDetailsTxIndex/rpc_polling_enabled (10.28s)
        bitcoind_test.go:126: unable to establish connection to bitcoind: method did not return within the timeout

[guggero]

I'm not sure if it's actually a question of how long we wait. A lot of tests fail on my local machine because there are port collisions. So I think this will likely be fixed with #8273 (which I should look into to fix the new failures that popped up now).

[yyforyongyu]

I'm not sure if it's actually a question of how long we wait. A lot of tests fail on my local machine because there are port collisions. So I think this will likely be fixed with #8273 (which I should look into to fix the new failures that popped up now).

yeah i also saw port collision sometimes in lnd, but only during the shutdown process where the rpc port was not cleaned. Have not yet seen such a case in unit test tho.