fuzz: Set ignore_incoming_txs in p2p_headers_presync

This avoids non-determistic code paths.

Without this patch, the tool would report a diff:

cargo run --manifest-path ./contrib/devtools/deterministic-fuzz-coverage/Cargo.toml -- $PWD/bld-cmake/ $PWD/../qa-assets/fuzz_corpora/ p2p_headers_presync 32

...
- 5371|    393|        peer.m_next_send_feefilter = current_time + m_rng.randrange<std::chrono::microseconds>(MAX_FEEFILTER_CHANGE_DELAY);
- 5372|    393|    }
+ 5371|    396|        peer.m_next_send_feefilter = current_time + m_rng.randrange<std::chrono::microseconds>(MAX_FEEFILTER_CHANGE_DELAY);
+ 5372|    396|    }
  5373|  16.2k|}
...

Author: MarcoFalke

src/test/fuzz/p2p_headers_presync.cpp

@@ -31,6 +31,9 @@ class HeadersSyncSetup : public TestingSetup
         PeerManager::Options peerman_opts;
         node::ApplyArgsManOptions(*m_node.args, peerman_opts);
         peerman_opts.max_headers_result = FUZZ_MAX_HEADERS_RESULTS;
+        // No txs are relayed. Disable irrelevant and possibly
+        // non-deterministic code paths.
+        peerman_opts.ignore_incoming_txs = true;
         m_node.peerman = PeerManager::make(*m_node.connman, *m_node.addrman,
                                            m_node.banman.get(), *m_node.chainman,
                                            *m_node.mempool, *m_node.warnings, peerman_opts);