url: skip to-be-closed connections when pipelining (follow-up)

- Change back behavior so that pipelining is considered possible for
connections that have not yet reached the protocol level.

This is a follow-up to e5f0b1a which had changed the behavior of
checking if pipelining is possible to ignore connections that had
'bits.close' set. Connections that have not yet reached the protocol
level also have that bit set, and we need to consider pipelining
possible on those connections.

lib/url.c

@@ -2908,7 +2908,8 @@ static bool IsPipeliningPossible(const struct Curl_easy *handle,
                                  const struct connectdata *conn)
 {
   /* If a HTTP protocol and pipelining is enabled */
-  if((conn->handler->protocol & PROTO_FAMILY_HTTP) && !conn->bits.close) {
+  if((conn->handler->protocol & PROTO_FAMILY_HTTP) &&
+     (!conn->bits.protoconnstart || !conn->bits.close)) {
 
     if(Curl_pipeline_wanted(handle->multi, CURLPIPE_HTTP1) &&
        (handle->set.httpversion != CURL_HTTP_VERSION_1_0) &&
@@ -3283,8 +3284,8 @@ ConnectionExists(struct Curl_easy *data,
       pipeLen = check->send_pipe->size + check->recv_pipe->size;
 
       if(canPipeline) {
-        if(check->bits.close)
-            continue;
+        if(check->bits.protoconnstart && check->bits.close)
+          continue;
 
         if(!check->bits.multiplex) {
           /* If not multiplexing, make sure the pipe has only GET requests */