NFSv4.1 server deficiencies fixed for ESXi client

Hi,

Since I posted w.r.t. issues that seem to violate the RFC, I figured I should also
post ones that identified deficiencies in the FreeBSD server. These have either
been patched in head/current or will be soon and will be MFC'd.

- BindConnectiontoSession wasn't implemented. It is never used by the FreeBSD
  client and not used during normal operation of the Linux client.
  --> Now in head and will be MFC'd soon.
- OPEN_SHARE_ACCESS_WANT_NO_DELEG flag generated an error when set for
  OpenDowngrade. Since OpenDowngrade never issues a delegation, no other client
  sets this flag. However, since the RFC doesn't forbid it, the code in head now just
  clears/ignores the flag instead of generating an error.
- ESXi client generates warnings that "2" is not a valid reason for not issuing
  a delegation. Since "2" is in the list and the RFC says nothing about when each
  reason is used, I don't know why it thinks it isn't valid. However, a patch that changes
  the reason makes it happy and since other clients don't seem to care, this patch
  will probably go in head soon.
  (Until then, all it does is generate warnings.)
  
rick