Tests that rely on `bitcoind` fail on MacOS

[danielgranhao]

Not sure if this is specific to MacOS, but the tests that rely on bitcoind are failing with:

thread 'btc_reverse_claim_relative_fee' panicked at tests/test_framework/mod.rs:43:14:
called `Result::unwrap()` on an `Err` value: JsonRpc(Transport(SocketError(Os { code: 35, kind: WouldBlock, message: "Resource temporarily unavailable" })))

Failed test list:

failures:
    btc_reverse_claim
    btc_reverse_claim_relative_fee
    btc_reverse_claim_size
    btc_submarine_refund
    btc_submarine_refund_relative_fee
    btc_submarine_refund_size

My assumption is that this is something specific to MacOS because tests run fine in CI.