Expose GSSAPI::Simple keytab

[hunzinker]

GSSAPI::Simple supports kerberos keytab by default. This PR exposes a client attribute kerberos_keytab which defaults to nil.

Addresses issue: #15

[hunzinker]

@kzk Hi! Anything else I need to do to get this merged?

Thanks

[tagomoris]

@hunzinker I'm very sorry for late reply.
Is this patch working on your site?

[hunzinker]

@tagomoris yes I've tested this against a cluster with Kerberos enabled and everything worked fine.

[tagomoris]

@hunzinker Okay, i'll merge this and release next version tomorrow (in my timezone) if i can find time to do it. :P
Thank you for contribution!

[tagomoris]

I've just released v0.7.1. Thanks!

[hunzinker]

Thanks!

cc\ @PaulOstazeski @p5k6

[redbaron4]

Hi @hunzinker I know this is an old thread and thank you for adding this feature.

However, trying to provide a keytab file without doing a kinit first leads me to a No Credentials provided error. See #32 issue for a description of what causes this issue.

Have you been able to authenticate without doing a kinit and by just providing the keytab file?