Fixes NTLM and Negotiate auth assertion "RefCountCount() == 2"

Fixes NTLM and Negotiate auth assertion "RefCountCount() == 2"

It turns out the replay cache and invalid RefCount cases this was added to
protect againt are not present anyway. After some minor cleanup to remove
double-calls in Negotiate things appear to run nicely.

NOTE:
 There is still a risk that these problem cases may in future occur, but
 meanwhile we need NTLM and Negotiate to be usable and efficient.
 The bugs resulting from those can be dealt with if/when they do occur.