libstore: use proper connection handle for narFromPath

this could've just ignored exceptions thrown by the remote. in the
current implementation there's no way such an exception could have
propagated to the client though, so there's no change in behavior.

Change-Id: Ide03bda1cb0ad7fb5f27b4ee5d16efd6c2b635ba

lix/libstore/remote-store.cc

@@ -734,7 +734,7 @@ RemoteStore::Connection::~Connection()
 
 kj::Promise<Result<box_ptr<Source>>> RemoteStore::narFromPath(const StorePath & path)
 try {
-    auto conn(TRY_AWAIT(connections->get()));
+    auto conn(TRY_AWAIT(getConnection()));
     conn->to << WorkerProto::Op::NarFromPath << printStorePath(path);
     conn->processStderr();
     co_return make_box_ptr<GeneratorSource>([](auto conn) -> WireFormatGenerator {