Spnego on the 'server' end of security=server just does not work, so set the

Spnego on the 'server' end of security=server just does not work, so set the
flags so we just do a 'normal' session setup.

Also add some parinoia code to detect when sombody attempts to do a 'normal'
session setup when spnego had been negoitiated.

Andrew Bartlett
(This used to be commit 190898586fa218c952fbd5bea56155d04e6f248b)