ipc: Handle bitcoin-wallet disconnections

This fixes an error reported by Antoine Poinsot <darosior@protonmail.com> in
https://github.com/bitcoin-core/libmultiprocess/issues/123 that does not happen
in master, but does happen with https://github.com/bitcoin/bitcoin/pull/10102
applied, where if the child bitcoin-wallet process is killed (either by an
external signal or by Ctrl-C as reported in the issue) the bitcoin-node process
will not shutdown cleanly after that because chain client stop()
calls will fail.

This change fixes the problem by handling ipc::Exception errors thrown during
the stop() calls, and it relies on the fixes to disconnect detection
implemented in https://github.com/bitcoin-core/libmultiprocess/pull/160 to work
effectively.

src/init.cpp

@@ -33,6 +33,7 @@
 #include <interfaces/ipc.h>
 #include <interfaces/mining.h>
 #include <interfaces/node.h>
+#include <ipc/exception.h>
 #include <kernel/caches.h>
 #include <kernel/context.h>
 #include <key.h>
@@ -298,6 +299,14 @@ void Shutdown(NodeContext& node)
     StopREST();
     StopRPC();
     StopHTTPServer();
+    for (auto& client : node.chain_clients) {
+        try {
+            client->stop();
+        } catch (const ipc::Exception& e) {
+            LogDebug(BCLog::IPC, "Chain client did not disconnect cleanly: %s", e.what());
+            client.reset();
+        }
+    }
     StopMapPort();
 
     // Because these depend on each-other, we make sure that neither can be
@@ -370,9 +379,6 @@ void Shutdown(NodeContext& node)
             }
         }
     }
-    for (const auto& client : node.chain_clients) {
-        client->stop();
-    }
 
     // If any -ipcbind clients are still connected, disconnect them now so they
     // do not block shutdown.