MINOR: http: prevent smp_fetch_url_{ip,port} from using si->conn

MINOR: http: prevent smp_fetch_url_{ip,port} from using si->conn

These two fetch methods predate the samples and used to store the
destination address into the server-facing connection's address field
because we had no other place at this time.

This will become problematic with the current connection changes, so
let's fix this.