rpc: socket: Don't repeatedly attempt to launch daemon
    
    On every socket connect(2) attempt we were re-launching session
    libvirtd, up to 100 times in 5 seconds.
    
    This understandably caused some weird load races and intermittent
    qemu:///session startup failures
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1271183