SPNEGO should be handled within libgssapi proper, we should handle only real mechanisms. So we will need to always filter out spnego from the mechnisms lists in the client mechglue.
This was solved by changing the way interposer plugins work (they have to specify what mechanisms to use) and spnego is not currently forwarded, so we can close this.
Metadata Update from @simo: - Issue set to the milestone: X - DEFERRED