Set "Connection: close" for non-keep-alive requests

According to the HTTP 1.1 Spec:

> An HTTP/1.1 server MAY assume that a HTTP/1.1 client intends to
> maintain a persistent connection unless a Connection header including
> the connection-token "close" was sent in the request. If the server
> chooses to close the connection immediately after sending the
> response, it SHOULD send a Connection header including the
> connection-token close.
https://www.rfc-editor.org/rfc/rfc2616#section-8.1.2.1

The Node.js `Request` module depends on getting the header `Connection:
close` to properly sequence socket messages, otherwise it throws a
"socket hang up" error.

This issue was found due to Remix having a custom implementation of
`fetch` that use's Node.js's `Request` module, which has different
behavior than the native Node.js `fetch` global.

edb/server/protocol/protocol.pyx

@@ -360,7 +360,7 @@ cdef class HttpProtocol:
             response.content_type,
             response.custom_headers,
             response.body,
-            response.close_connection)
+            response.close_connection or not request.should_keep_alive)
 
     def _switch_to_binary_protocol(self, data=None):
         binproto = binary.new_edge_connection(