url: keep bit.user_passwd untouched when re-using connection

While connections for HTTP don't actually have credentials (unless using
NTLM horrors), we maintain that info in there for now and just make sure
to not reset it when a connection is reused.

Fixes #8449
Reported-by: John H. Ayad

lib/url.c

@@ -3485,7 +3485,6 @@ static void reuse_conn(struct Curl_easy *data,
 
   /* get the user+password information from the old_conn struct since it may
    * be new for this request even when we re-use an existing connection */
-  conn->bits.user_passwd = old_conn->bits.user_passwd;
   if(conn->bits.user_passwd) {
     /* use the new user name and password though */
     Curl_safefree(conn->user);