Compass crashes after a successful authentication to kerberos.

The authentication with kerberos gets triggered multiple times inside the driver on MongoClient.connect, however the GSSPI code in the driver is not meant to deal with concurrent calls as that seems to break the state of the authentication completely.

Doing a serialisation of the authentication and reusing the same state for the same requests seems to fix it.

The setup to reproduce the issue and a possible fix is in this gist:
https://gist.github.com/mcasimir/1d89b8fa81c8fed51f387f394abe6c51