Fix flaky test_trampoline_single_hop_receive test

[tnull]

In #3623 we discovered that test_trampoline_single_hop_receive is flaky, likely depending on a particular EntropySource output.

If we call entropy_source.get_secure_random_bytes() in ChainMonitor's block connection code, test_trampoline_single_hop_receive fails with:

node 0 DEBUG [lightning::ln::onion_utils:1249] Invalid HMAC in attribution data for node at pos 0
node 0 TRACE [lightning::ln::outbound_payment:2244] Failing outbound payment HTLC with payment_hash 66687aadf862bd776c8fc18b8e9f8e20089714856ee233b3902a591d0d5f2925
node 0 TRACE [lightning::ln::channelmanager:11511] Handling event PaymentPathFailed { payment_id: Some(66687aadf862bd776c8fc18b8e9f8e20089714856ee233b3902a591d0d5f2925), payment_hash: 66687aadf862bd776c8fc18b8e9f8e20089714856ee233b3902a591d0d5f2925, payment_failed_permanently: false, failure: OnPath { network_update: None }, path: Path { hops: [RouteHop { pubkey: PublicKey(236cdaa42692b2c9dcaa1e9755b09f01015badea0cbd02b6162d328a23d2f8550b2875c8c2a0382aa31936f841ca09946202c0c6d5177ed9a1234ff4969b49db), node_features: [], short_channel_id: 1099511627776, channel_features: [], fee_msat: 1000, cltv_expiry_delta: 48, maybe_announced_channel: false }, RouteHop { pubkey: PublicKey(ce1dc610d880181464ae9a76568387c1fd3839d8af69f74012d241f33d2e8f88c4e526dbe59946cf190e949a2c5f92bafcccce5aa9708d2455d18231162afeb5), node_features: [], short_channel_id: 12094627971072, channel_features: [], fee_msat: 0, cltv_expiry_delta: 48, maybe_announced_channel: false }], blinded_tail: Some(BlindedTail { trampoline_hops: [TrampolineHop { pubkey: PublicKey(ce1dc610d880181464ae9a76568387c1fd3839d8af69f74012d241f33d2e8f88c4e526dbe59946cf190e949a2c5f92bafcccce5aa9708d2455d18231162afeb5), node_features: [], fee_msat: 1000, cltv_expiry_delta: 24 }], hops: [BlindedHop { blinded_node_id: PublicKey(e425f629dfaafc9c40c92932546ec17aa84606be5b5ecec24683331eef75e7a79b48b40c5290cf0a05c651b2a1d9fe5a392035e3b9f80552cf5ab1a36d6b6727), encrypted_payload: [27, 215, 137, 83, 5, 227, 231, 162, 4, 182, 46, 244, 76, 204, 219, 75, 124, 56, 46, 180, 104, 46, 225, 92, 161, 49, 221, 129, 185, 0, 247, 67, 94, 116, 128, 128, 160, 41, 2, 201, 41, 162, 62, 221, 250, 126, 119, 51, 81, 254, 248, 159, 209, 59, 160, 252, 175, 216, 31, 184, 193, 11, 5, 144, 166, 80, 200] }], blinding_point: PublicKey(588125d5825b65016232a0ff30868bc396351d6813680799377603d40391296c7794d2a56ae95ba85a20c1c2450a6068a19ebc3c3fcd4b54473fd1214b19a399), excess_final_cltv_expiry_delta: 39, final_value_msat: 1000 }) }, short_channel_id: Some(1099511627776), error_code: None, error_data: None }...
node 0 TRACE [lightning::ln::channelmanager:11511] Done handling event, result: Ok(())
node 0 TRACE [lightning::ln::channelmanager:11511] Handling event PaymentFailed { payment_id: 66687aadf862bd776c8fc18b8e9f8e20089714856ee233b3902a591d0d5f2925, payment_hash: Some(66687aadf862bd776c8fc18b8e9f8e20089714856ee233b3902a591d0d5f2925), reason: Some(RetriesExhausted) }...
node 0 TRACE [lightning::ln::channelmanager:11511] Done handling event, result: Ok(())

thread 'ln::blinded_payment_tests::test_trampoline_single_hop_receive' panicked at lightning/src/ln/functional_test_utils.rs:2586:13:
assertion `left == right` failed: unexpected payment_failed_permanently value
  left: false
 right: true
stack backtrace:
   0: __rustc::rust_begin_unwind
             at /rustc/e6ed56aad81a8bc50c403535370164132e96bb08/library/std/src/panicking.rs:697:5
   1: core::panicking::panic_fmt
             at /rustc/e6ed56aad81a8bc50c403535370164132e96bb08/library/core/src/panicking.rs:75:14
   2: core::panicking::assert_failed_inner
   3: core::panicking::assert_failed
             at /rustc/e6ed56aad81a8bc50c403535370164132e96bb08/library/core/src/panicking.rs:380:5
   4: lightning::ln::functional_test_utils::expect_payment_failed_conditions_event
   5: lightning::ln::functional_test_utils::expect_payment_failed_conditions
             at ./src/ln/functional_test_utils.rs:2640:2
   6: lightning::ln::blinded_payment_tests::do_test_trampoline_single_hop_receive
             at ./src/ln/blinded_payment_tests.rs:2166:4
   7: lightning::ln::blinded_payment_tests::test_trampoline_single_hop_receive::{{closure}}
             at ./src/ln/blinded_payment_tests.rs:2172:40
   8: core::ops::function::FnOnce::call_once
             at /rustc/e6ed56aad81a8bc50c403535370164132e96bb08/library/core/src/ops/function.rs:250:5
   9: core::ops::function::FnOnce::call_once
             at /rustc/e6ed56aad81a8bc50c403535370164132e96bb08/library/core/src/ops/function.rs:250:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

(cc @Arik)