Ticket 47426 - move compute_idletimeout out of handle_pr_read_ready
    
    Description:  Instead of calculating the idletimeout everytime new data is received,
                  set the anonymous reslimit idletimeout and handle in the connection struct when the
                  connection first comes in.  Then update idletimeout after each bind.
    
                  I removed compute_idletimeout() because bind_credentials_set_nolock()
                  basically does the same thing, so it was just extended to update
                  the idletimeout.
    
    https://fedorahosted.org/389/ticket/47426
    
    Reviewed by: richm(Thanks!)
    (cherry picked from commit ed83a783887b0f9c54781bac64c7b26f0402640a)
    (cherry picked from commit d4f9c40d6d7f36b31e81c2326036a65229fe470f)