Make TlsNetworkAddress::connect() not require to stick arouncd.

Although contrary to conventions, it's surprisingly easy to write code that calls connect() and then drops the address before the connection completes, and such code works with the default network implementation, so let's accept it.

c++/src/kj/compat/tls.c++

@@ -132,8 +132,7 @@ public:
       throwOpensslError();
     }
 
-    return sslCall([this]() { return SSL_connect(ssl); })
-        .then([this,expectedServerHostname](size_t) {
+    return sslCall([this]() { return SSL_connect(ssl); }).then([this](size_t) {
       X509* cert = SSL_get_peer_certificate(ssl);
       KJ_REQUIRE(cert != nullptr, "TLS peer provided no certificate");
       X509_free(cert);
@@ -386,9 +385,15 @@ public:
       : tls(tls), hostname(kj::mv(hostname)), inner(kj::mv(inner)) {}
 
   Promise<Own<AsyncIoStream>> connect() override {
-    return inner->connect().then([this](Own<AsyncIoStream>&& stream) {
-      return tls.wrapClient(kj::mv(stream), hostname);
-    });
+    // Note: It's unfortunately pretty common for people to assume they can drop the NetworkAddress
+    //   as soon as connect() returns, and this works with the native network implementation.
+    //   So, we make some copies here.
+    auto& tlsRef = tls;
+    auto hostnameCopy = kj::str(hostname);
+    return inner->connect().then(kj::mvCapture(hostnameCopy,
+        [&tlsRef](kj::String&& hostname, Own<AsyncIoStream>&& stream) {
+      return tlsRef.wrapClient(kj::mv(stream), hostname);
+    }));
   }
 
   Own<ConnectionReceiver> listen() override {